The bug finally hit me. No travels to other lands, consignment vendor is still the same, and it was within operating hours. Sent my sim to sell some more produce, and didn't have the option to buy. Used the remove consignments, and there were 3 items left from a previous consignment, one which had "days" listed a negative 1. When I removed the three, I was then unable to buy at all. Fortunately I wasn't trying the self-employed career at the time, and can still sell at the grocery store and from inventory.
Edit: Okay, checked today, and I can consign stuff again. Only thing I did before loading today was delete all my cache files. Maybe when I removed the -1 consigned item, it needed a day to reset the vendor. Added some new stuff, I'll keep an eye on it.