Ethical obligations to inform a company that didn't deposit a check?

I had an HVAC company come to do some repair work in early November. The guy did the work, and I wrote him a check. He emailed me a receipt, which I have. So both of us – me and the company – acknowledge that I paid.

It’s now just under two months later. The check has never been negotiated or deposited; it has not shown up as paid on my checking account.

In Georgia, checks are not considered ‘stale’ for six months, so there’s no issue with that.

Ethically, do I have an obligation to phone the HVAC people and say “you guys really ought to cash the check”?

I don’t think I do, because the responsibility is theirs. But it’s a little grey for me.

What’s the collective wisdom?