crocea clam question

[oilers1]

HI, I need some info; I have had a crocea clam in the tank for about2 weks, It came mounted on a large piece of rock. I put the rock and the clam in the middle of the tank. I woke up this morning seeing the clam on the sand with out the the rock. the only thing left on the rock was a large strands of white tissue, my question is this could the clam cut itself off or was there damage done to the bissal gland, the clam is open right now, so any info would be appreciated.