Memories are funny things. Sometimes they stick around forever, and other times they are gossamer and fade away quickly, seemingly without reason as to why one or the other happens. It's further complicated by the fact that every time you open a memory and examine it, then put it away, you get your "fingerprints" all over it, changing it slightly. Studies have shown that the more you revisit a memory, the more it drifts from the original.
Hypnosis can help you remember the password for your Bitcoin wallet or find your lost car keys if the conditions are right and it often works great! But if the memory has been corrupted, it's possible that it's gone forever.
If the information is still there and it's just buried, hypnosis is often your best bet for retrieving it.