Congratulations!
You've had some good advice, I'd also go down the nice meal route, make a bit of an effort with things he likes and that make you both happy, but make it no pressure. Do it as a way of thanking him for his nice gesture and the pre-engagement ring and maybe get him something as a lovely token from you - cufflinks, or something maybe? No TV, no phones, lovely food and wine, and say you were taken aback by what he said but that nothing makes you happier than the idea of the two of you getting married and being together for the rest of your lives.
Ask, gently, what exactly he meant by the ring, I'd assume it was a token to give you at the time with his intention being to then choose you a ring together. But leave it open in case that wasn't what he meant.
As PPs have said, sometimes a funny story (if you can turn it into one by following it with a special evening where you agree you're now engaged) is better than a picture perfect proposal!
My own experiences, when my first husband proposed to me we'd already discussed getting married but were both quite relaxed, he waited till it had snowed one evening, then filled the garden with glass jars (still not sure where he'd got them all) with night lights, asked me to come and look at something in the garden and got down on one knee and asked me to marry him. Pretty perfect in a Richard Curtis sort of way. He knew not to ask anyone for permission, my Dad would have decked him and I'd have been very unimpressed, it would have shown he didn't know me at all. As it was, my parents were very happy about the whole thing anyway!
But the marriage had little to recommend it, he turned into an arse and we were divorced a couple of shit years later.
I recently got married again and there was no proposal. We'd both done it before, there was no fuss, no candles, no flowery words. But the man, relationship and marriage are totally different and it felt right to quietly, calmly decide that getting married was what we both wanted and felt absolutely right.
In a way I hadn't expected, when people gradually found out we were getting married I spent a lot of time saying no, he didn't ask me and there wasn't a proposal, we decided to do it and have picked a date. People were surprised but they got it!
I'm divorced, in my 30s and if I was going to get married again I wanted a proper discussion about what it meant. Which felt a lot more romantic than following the romcom path of a butt load of fuss and the woman getting little say in the matter.
It sounds like you have a good, solid relationship and both really want to be together. I hope you manage to work things out. As PPs have said, it probably didn't go how either of you had imagined but it's easily salvageable and you just need to talk to each other.