Did you get an answer to this? If not, it looks like an old Sedum that I have, but don't know it's name.

From this small sample, it could be Sedum sarmentosum or Sedum acre, both commonly called gold moss sedum. Larger clumps are easier to tell apart.

Yes, I have been told mine is probably Acre, I got it from an older lady in the early 1970's I also found one that is nicknamed Graveyard sedum as it is in so many graveyards which appears to be Acre, gold moss sedum.

That looks like Sedum sarmentosum to me rather than Sedum acre, but a photo with something to reference the size would be helpful. Either way, to try to establish it, I'd pinch off the flowers and plant it somewhere less moist. Coming from a sidewalk crack, it's probably well adapted to less moisture. In fact, I'd probably just set it on the top of the soil and mulch with some gravel to keep the leaves relatively dry while it roots in.

Edited to add, this is all probably moot at this point -- either it made it back in May or it didn't! With this sedum, there is probably more back near where you got this one, though.