Sorry for my delayed response. This is really just too easy... let us continue.
I don't see anything inherently unhealthy about this scenario.
Uh huh... nothing at all unhealthy about it.
Note that you are contradicting yourself a bit here. Either the 100 BTC associated with that dusty address were not "lost", since they were recoverable in which case they should have been considered part of the currency supply, or they were lost and then were "re-mined" by the person who dusted off the private keys, which is an ability you are saying is "superior".
There are several faulty lines of logic used here. First of all the bitcoins were lost for a long time, but they were found again when the person found the private key in a dusty box. This is not really how bitcoins are lost, they are lost when private keys are destroyed and not recoverable. However, in this case, the private key was written down physically so it was possible to find it again. At this fictional point in the future, it will have been a very long time since the market saw any single account holding such a large amount of bitcoins. As far as the market is concerned, there is essentially only 100 bitcoins in active circulation. Also keep in mind that I am describing bitcoin as it is now, where coins cannot be re-mined, to illustrate why infinite deflation is unhealthy. Reintroducing an amount of coins which appears to be equal to the entire amount left in circulation after hundreds or thousands of years of deflation in the money supply, is going to cause some large upsets. Now in the case where it's possible to re-mine coins, if that person found the key sitting in an old dusty box, and it had remained untouched for over 100 years, the coins would already be gone. In fact if he found those coins 99 years after they were first active, he could use them; but in such a scenario the re-mining process has ensured a stable money supply, meaning his newly acquired 100 bitcoins will have no dramatic effect on the market because there are still nearly all bitcoins in circulation.
Imagine a scenario where gold has been lost into the deepest part of the ocean over time until there is only 100 kilograms of gold left in active use in the world. Now imagine someone opens an old dusty trunk in the attic and finds 100 kg of gold. Same thing.
Once again this is not the "same thing". When bitcoins are lost they become inaccessible. Gold at the bottom of the ocean is still accessible to those who have the motive. We drill oil from some insanely deep places. And if we lose a majority of our gold in the ocean, there's going to be an extremely big motive for people to go get it. Furthermore, and more importantly, it's very unlikely that we will ever lose a considerable amount of gold in a place which makes it virtually impossible to recover. Bitcoin is entirely different. It's extremely easy to lose with one wrong move, and any single time that any amount of BTC is lost, it goes into a state where it's virtually impossible to recover. Nearly every time we lose gold it's going to be in a state where it's fairly easy to recover. So there are clearly some huge flaws in this analogy, just like all your other analogies.