We all have the naive impression that memory is somehow like a video recording and we can just access it to find out what happened. Indeed, we all have some very vivid and probably quite accurate memories about some exceptional events, or can recall exactly what page and what part of the page we read some specific item. There area also examples of amazing memory stunts and records, and even memory contests and championships.
But we cannot assume that just because we have some very good memories, memory is generally good, indeed, it is mostly pretty bad, especially compared to any kind of recording system.
This is supported by several areas of research demonstrating how easy it is to plant fake memories, reshape memories, and get people to be completely convinced that they are describing are exact and real.
One area of research is eyewitness testimony, which has pretty much been the standard in courts since courts existed, yet when eyewitness accounts are compared, they almost always come up with a variety of contradictions.
There's also been research into the phenomena of "found" or "recovered" memories often used to convict accused child abusers. Again, it turns out that suggestion and guidance on the part of the investigator can create things our or whole cloth, so it must be very carefully guarded against.
There's also several other research areas in which this is relevant, but the outcome is pretty consistent -- human memory is generally pretty bad (sorry I haven't got the time to track down the references).
I've found that it's best to just treat memory as merely a good hint about what might have happened (or where I might have left that tool or the keys), and then look for actual evidence of what really happened.