1) You're very much correct in that the core issue here wasn't determined or resolved, due to the fact that we can't/don't know what exactly caused this problem in the first place. However, the user was able to recover the sticky notes, so the issue of them being lost was fixed. We could certainly continue to discuss the circumstances surrounding this loss if the OP were to continue to post in here, but that often does not happen once an issue is solved to the point of at least being able to move on in terms of productivity on the machine. The thread being marked solved is the choice of the user, obviously, so we depend on their feedback as to whether or not they are satisfied with the responses thus far or whether discussions need to continue. So, there's not much we can do if the OP has moved on. Perhaps they will return to the thread here.
2) I was referring to the following quote on my response:
mgross333 said:
I also, based on 7 years experience fixing PCs, do not think that the SFC /scannow approach will fix ANYTHING.
So, I was pointing out how many people's experience on this forum is quite contrary to your opinion of that, regardless of any later qualifying or contradictory statements.
The chance of file corruption occurring in a short period probably is very low, but that doesn't mean you rule it out. With a state of the art Sony laptop that costs that much with all of that fast storage, running SFC would take little to no time and could be run in conjunction with whatever else you're doing. Personally, I don't see any reason not to run it as it can only help, but it is obviously a judgment call. It's unfortunate you haven't had any useful experiences with running it in the past, but many people here have, so I hope you continue to give it a chance as it's a rather useful tool provided by Microsoft.
It is possible that this issued was caused by a Windows Update. No one is ruling that out. It could be, it could not be. It's just as likely as a corrupt system file, though, as they aren't mutually exclusive things. Either can cause issues at any point. Or, it could be something else we're not considering. The bottom line is that you are attempting to make an educated guess based on your experiences just as everyone else is doing on here. Obviously, no one thus far has a direct response as to the particular reason the stickies disappeared in this case, but we can continue to search. Personally, I'm surprised you posted to the Experts Exchange forum as I don't believe very many people have much luck on there, myself included in the way past before I realized what a dearth of help it was. Although you might be frustrated with responses so far on here, I would argue that this forum provides orders of magnitude more help than that one.