I had this too, brought some credits (around $50USD) around Christmas time and only used a small amount, went to look the other day and it showed me a balance of zero, also couldn't figure out what happened to them
Small enough amount of money that I didn't bother chasing it up, but surprising to see other people saying the same thing, maybe I will
file a ccpa data access request, they either have data to backup the usage (and must release it) or they don't have it (and should fix the issue)
Some time ago I found out that OpenAI API balance gets wiped out after a year. Still bitter about it, telecom operator shit and it’s giving me the creeps when sama talks about AI being like an utility. Good luck.
OpenRouter expired my credits because they were "too old" (more than 12 months old). Didn't realize credits would rot like that.