Yes, we have found the Adquipecten muscosus on Sanibel.  Ken found one this
winter and we found five or six last year.  The one he found this year was
rust colored which seems to be the most common to find.  We find numerous 
rust halves and occasionally a yellow or orange half.  Last year the found
whole ones we found were rust, plus an orange and a reddish one, as well.  
These have been found on the beach following NW winds that have brought in
a lot of calico scallops (Argopecten gibbus).
 
Joyce Matthys
Sanibel Island/Salem, Oregon