Has this ever happened to anybody?

You go into the skills menu and see your health in green (might be magicka or stamina, but in my case it was health), indicating that you have a health buff of some kind. You don't know what it is so you go into the magic effects menu and run down the list. But you find nothing indicating increased health. You haven't taken any potions, visited any shrines, and you're not wearing any items that would do this. But just to make sure, you sleep for about six days so that any effects like that would certainly wear off. And then when you're all done you go back into the stats menu and find you still have a health increase?

This happened to me the other day. I couldn't figure it out. My base health was 200 but it said 208 in green. And we all know that ANY stat increase should appear in the magic menu, but it didn't.

Even though it was in a way a "positive" bug (if in fact it was a bug), I suppose it could've just as easily been a negative one of -8 health. In any case, when this happened, I felt as though I lost control of the game. I couldn't explain it or pinpoint it. That bothers me. Has anyone else encountered this?

By the way I do play with a lot of mods but none that would have any effect on stats like that.

Did you cook and eat anything that might have caused a lingering effect? If it stays that way I say just go with it. Hell the other day I fast traveled somewhere and when I spawned in I was immediately attacked by a falmer...above ground, outside, during the middle of the day! Things like that make me go...hmmmmm?!!!!

Oh no, no cooking for me. Not ever.

Never had the outside-daytime-falmer situation like you describe though. If you're on the PC you can check in the CK to see what's supposed to spawn in that area and how it happened (or if you're not playing on PC you can ask someone here to look for it). That bug at least sounds somewhat traceable. With stat-based errors (if that's what it was) I wouldn't even know where to begin looking for the culprit.

LOL....I'm the same way. I think I cooked something so I could get the trophy but that was it. I'm on the PS3 and that falmer inccident was the 2nd of two interesting outside encounters. The 1st was a deathlord that attacked me when I fast traveled to Goldenglow Estate. Weird but I just keep on keeping on. Sorry as I know none of this helps your health boost question and like you said I would not know where to begin.

Sleeping for 6 days does not advance many of the active effects timer.

I noticed this recently with the blessing of talos. The timer does not move when you fast travel, or when you sleep. But if you do regular travel across the land, it goes away quickly.

To exploit this, I travel to a tough dungeon and find the place so that I can fast travel back to it, then go to College of Winterhold and clean one of the focal points, not all 3, and fast travel back and clear the dungeon with infinite magicka reserve.

Question, do you use conjuration? If so there is a minor glitch tied to the skill. I think it works like this.... if you use conjuration to bring back to life a minion excessively then every time you fast travel or just load into a cell what ever you raised from the dead in the couple cells that you visited before hand will load with you. There have been reports on the 360 side of people loading into a cell after fast traveling to find 5-6 dragur, or 5-6 bandits and bandit chief or a combination of what ever waiting for them. Sounds like a cool bug if your frame rate holds up

I do from time to time to mess around after a battle or two. But what you mention sounds very plausible. Currently my character sits at level 72 with about 430hrs and my frame rate seems to be holding quite nicely. I will keep an eye out for more of these interesting encounters for sure.

Google translate shows 'bezit'.

This is a bug with fortify potions and magical effects (health, magicka, stamina). I can't remember the exact details, but when you use a fortify potion (or have a fortify effect active) and your stat drops below your normal level, the fortify effect protects you from dying. If the fortify effect wears off while you are below normal, you get a permanent buff to your stat. Sorry if it's a bit confusing, I'm trying to find the exact reference.