When I entered the deli, there was a piece of poop on the ground. I picked it up. The shopkeeper pig ran to me to give me an oinc, but as she went to hand it to me, she disappeared.
After she disappeared, I couldn't buy food from the deli.
Tried save/quitting then re-opening the game, but she still wasn't there.
1. Enter deli. 2. Pick up piece of poop. 3. Wait for shopkeeper pig to try and give you an oinc.