Clam type thing

[Leedowlrods]

Last night I found a closed clam type thing on my sea bed, this morning I found it opened up and empty!! Could/would a cleaner shrimp do this? I don't think it was my hermits as they don't seem to have moved much
It Defo wasn't my two clown dish either
....

 

[Leedowlrods]

Before

 

[Leedowlrods]

After...

 

[Convict2161]

Looks dead to me, I have a few little ones laying around my sand bed.