I had three crude swords in a row vanish the moment I attack something with them.
I crafted a Homewrecker and was blocking shots from a rat just fine (Got the messages about blocking with my homewrecker).
Went back to the rats a day later, swung at one, and my homewrecker vanished.
Homemade crowbars aren’t vanishing. Just killed two rats. So the crude sword and the homewrecker bugged out for me. =/
You sure they didn’t stick to the enemy?
I’ve noticed occasionally a weapon will get stuck and the notification message gets pushed off screen by combat messages and it disappears until the critter is dead.
Well either they are on the ground or stuck to the enemy like said above so may want to check that as that happens with some weapons.
I guess that’s possible, although I checked my message log to see if I got any notifications. Just me swinging (missing), and then unarmed attacks from that point. But it’s always possible.
Yeah possible it could be a new bug too so who knows, guess if it happens again or to someone else then we will know for sure 
My guess is the weapon is getting stuck. I’ve been playing a character with 13 strength and haven’t had this happen.