Where's Canada?

Went looking for blue-eyed Mary yesterday. In some unrelated research I discovered it had been collected in a woodlot near Morenci in the 1950's. Blue-eyed Mary has recently been listed as a threatened species in Michigan. I thought it would be interesting if it was still there. I couldn't find it. Coincidentally, Canada violet and Canada waterleaf were also missing. I had previously seen a lot of both of those at this site. Conversely, there were significantly more green violets (Hybanthus). The area seems to be undisturbed. There aren't even many invasives. So maybe this is all just random variation? Perhaps it even has something to do with this year's extended cool spring. An annual like blue-eyed Mary might just take a year off if things aren't right.