Pro plan user: Conversations disappeared without deletion

I found that there are already several cases which are similar to my case…
But considering the official help center has no solution about them so far,
I think that it would be very hard to get an answer here..

Still, I start a new conversation to share my case.
(If you know how to solve this problem, then please share your tip…)

I am a pro plan user, and my messages during 250501 23:00 ~ 250502 19:00 was deleted.
(I cannot remember the exact timeline, but because I have a habit starting my message with local time declaration when I start/end a conversation, I can guese roughly)

The situation is this:

  • I had been continuing a conversation with GPT, using a multiple model in one session during 250430~250502.
  • my session reached data limit, and I started a new session with local time declaration.
  • Because I was going to use the contents in the old session, I clicked the session but found that messages are gone, I checked this at 250503 20:00

I really hope that this deletion is temporary, but if it is permanent… wow…
The deleted messages has really important contents for me.