The 2001 Silver Buffalo Dollar was successful (both unc and proof) but those were popular. The 2001 Silver Proof Set at one point was the second most valuable after the 1999 but again that was a fairly popular item. The other commemorative (Capitol Visitor Center) wasn't too popular but I don't recall prices ever going up for any of the versions. The only thing that comes to mind is one of the Platinum Eagles for that year. Is that the coin you referenced?
I know it may appear a defect on the coin, but actually it is just a crease in the polyethylene-coated cellophane in which the coin is cased. I'm pretty sure.
I predicted hardly anybody would buy them, particularly the gold. So I bought a boatload of 'em. And once the mintage was announced prices shot up like a rocket. Sold 'em all
That must have been one of those with a fairly short period of price gain (excluding any gain based on gold spot going up) as commemoratives in future years saw even lower mintages. Congrats on picking correctly and knowing the right time to sell!
At the time I think it was the 2nd lowest commem ever. And back then, gold was around $300 an ounce so the coins were cheap in that regard. Issue price was around $180 if memory serves. You also have to remember that 70s were selling for $700-$800 back then because that was before they changed the grading standards and 70s became beyond common. So the price increase lasted for several years. Even a MS69 sold for over $400 back then.
To a lesser degree but similar to: https://www.cointalk.com/threads/franklins-in-mint-sets-with-white-corrosion.351358/ No helping your coin unfortunately.
Possibly, but back then the Mint didn't accept order cancellation. Defective could be returned for replacement, but only as long as the replacement supply lasted. Only way to get your money back was if you ordered and they sold out and couldn't supply the product.