I just signed up for "snap deposit" myself. USPS and the bank were taking close to ten business days to record a mailed check. The first thing I thought of was your scenario. I rarely write checks and I usually keep good track of the ones I do and/or deposit and when I miss one I start checking seldom used pockets.
In the past as an independent contract sports official I have had a few checks languish in a uniform jacket as I seldom use one, since I am in sunny So CA. BUT I always call the check issuer to let them know I am depositing a stale check. On occasion they would ask to send a replacement check and I would tear the old one up....after I got the new one.
In God I trust, all others....check in hand.
Good for you, catching that.