Without seeing the animal in question, I would REALLY doubt if you left a million bucks on the table, or even a fraction of it.
Could it have been a new gene? Absolutely. Is it an incredibly high value gene?....probably not, but possible.
The banana/coral glow, albino, and pied.....those were million dollar genes in their day and it doesn't take a rocket scientist to figure out why....appeal. You see anyone of them and you just HAVE to have it.
....and if it makes you feel better I owned an entire Bitcoin in November and sold it in November.....Bitcoin proceeded to hit an all time high of $20,000 shortly afterwards........I left $16,000 on the table of guaranteed money. So don't kick yourself too hard, just learn from your errors.
Cheer up, life is crazy, and it's too short to constantly worry about money as well.