to think that my neighbour could have been murdered?

[Candymay]

I know it sounds rather dramatic and that’s why it’s an AIBU I suppose. I feel maybe I’m thinking too much about this.
Last week I posted here after finding my neighbour dead and I wasn’t able to save him. It appeared to be a drug overdose. The police were quick to decide it was not a crime scene therefore his friends could enter the home again etc.
(I’m worried about identifying myself here because I’ve posted about sensitive personal stuff in the past but I’ll have to give details so as not to annoy people here).
Here is some information and some of the odd things that are worrying me.
He was a young man and drug user but had lots of friends and a good life.
I noticed a smell from the house for a couple of days before we found him. When we found him he looked like he could have been dead a while (but I’m not sure about this). Things were quieter than usual for a couple of days at least and I had mentioned to my son that we hadn’t seen our neighbour at all.
The person who found him just before she came to get me called his close friend on the phone. She was crying and panicking. The friend told her he would be there in an hour. Why did he not suggest calling an ambulance or the police? He called neither.
I called the police.
This same friend did come to the house an hour later told the police he had seen the deceased man that morning and that he had definitely been alive a few hours before. He described where he was lying and exactly what he was wearing. I know this is accurate because I had been in the house with the body. What troubles me is why would he see his friend on the floor and leave him there? He said that he was alive and that he (the deceased) had waved at him and told him to leave. So he had left.
The front door was left unlocked. This is another odd thing. It makes me think that perhaps the friend forgot to lock the door because he had seen his friend dead and panicked? Or that he wanted to leave the door for someone else to easily find him.
There was food on the floor that had been dropped- presumably by the deceased. Why would the friend who saw him in the morning not have noticed this was amiss or cleaned it up?
Another close friend of the deceased left the country abruptly just before the body was found. He had sent a text to the other friend to ask him to check on the deceased to make sure he was ok. This was the reason the friend had visited in the morning. Surely the sight he was met with would be clear that the man was unwell and desperately needed medical attention?
We have since checked the flat completely and the deceased’s phone is missing along with his bank card and driving license.
The police are not investigating. They say it is an accidental overdose and that’s the end of the matter.
Please no one be nasty to me but I just find it all very strange and suspicious.
What do other people think?

And to those that say I’m making it exciting drama you’re very far from the truth. I’ve gone to great lengths to protect him IRL. It’s been quite terrifying at times and I’ve got so much compassion for addicts and their families. I know a lot about it. I honoured him until the end and am continuing to do so.
My concern here is just that the police seemed quick to close the case without checking things out but maybe- and hopefully- I’m wrong. I just don’t know how they work so I could be far from accurate on how I see it.
I hope I haven’t offended anyone or made people feel angry. Honestly i have nothing but compassion and concern.

Yep, police will take valuables and lock them away safely for collection by a family member. It can be a long process waiting for coroner's reports etc. The police might not have seemed interested in you but they DO know what they are doing and were probably stressed/trying to deal with the situation at hand. A lot of shady/odd/ridiculous behaviour occurs in drug users. It will all be looked into but the police won't divulge information freely to a neighbour.

Also, it was probably their three billionth call of the night so they might have run out of manners

Where was the lodger for a few days? Was he/she away?

I'd assume that the post mortem would give an indication on how long he had been dead when found and that the police will investigate further following that.

Have you got good support, it must've been very distressing finding him

There was a drugs death of my friends DDs boyfriend. He died at a party, the friends cleaned the flat from top to bottom and got rid of any drugs paraphernalia before calling police. I would say someone leaving the scene or doing similar would be more likely in order to try and erase any involvement.