Should this worry me?

[GameofPhones]

It has happened twice now. Two teenage lads come to my door, asking for a ball back they've kicked into my garden. I say ok I'll throw it back over the fence. I go into the garden to look for it, there is no ball. I open my garden gate to tell them I can't find it, but they are nowhere to be seen. I am wondering if this is some kind of burglar's ruse.

Sounds like they are trying to get entry to your house. I report to non emergency number.

Yes this definitely sounds like they may be looking for a way to gain entry into your house, possibly to also see if anyone else lives with you too... report it!

Sounds like distraction burglary, have you got a spy hole in your door, I wouldn't open it if you don't recognise them. If you do answer the door, lock the door before you go to the garden.