Dilemma

Yes, ask for it back.
Don't let him have it again.

Bit different if it had been his family’s ring.
Quite.

I wouldn’t have given it to him. Get it back. Cheeky bugger.

He sounds a bit of a cheapskate, get that ring back ASAP!

I hope he has not pawned it!

I too would be asking for it back.

I agree ask for it back.

Just say that you'd like to keep it safe until he's ready for it.
Don't ask him if he "minds".
Just state it as a fact.
That's what I'd do.

Ask for the ring back. Unless it is used for its intended purpose it does not belong to him.
He had no right to keep it.

Ask for the ring back, say that seeing as the proposal hasn’t happened you would like to hold onto such a precious heirloom, and that actually you would prefer to keep the ring which will be passed onto your DD by yourself, so he should in this case buy his own engagement ring for her.

If he ever got round to proposing, would your daughter think it was her ring? Very odd.

I would definitely ask for it back. I wonder if he still has it?

Trying to picture our SIL asking to use my mother’s engagement ring to propose to our daughter?

Bit different if it had been his family’s ring.

How odd!

And no, I wouldn’t have given him it.

Get the ring back.

I would ask him how the proposal went.

I’d be inclined just to mention it very discretely and casually, if you can get him alone, and ask him if he’s chosen a date to propose and if he umms and arrrs I’d be inclined to ask if he’d like you to take care of the ring til he’s “ready”.

I would definitely ask for the ring back..