When using a thief steal skill while holding the hammer in the colossus fractal, the hammer disappears but continues to stack the corruption counters on the player.
This is a blocking bug since it makes it impossible to get the hammer back once it is lost in this manner.
Edit: my specific experience occurred when using the “Rusty Scrap Strike” steal skill
I think it would also be a good idea to test the thief steal skills while holding other environmental weapons/bundles as well.