I would say it's unlikely, but still possible. Ich goes through 3 stages throughout its life. The first stage, a larval stage, leaves them immobile where they are settled or attached(?) to rock and such. If there are ich larvae attached to the shells of the hermits, then when the ich parasite reaches the second stage they would then be free swiming in your tank and could infect a fish (where it then spends it's third stage).
As I said, unlikely, but possible, as far as I know.
as far as how to handle it.. IMO
, wait until you find some at another LFS
. See if another LFS
, one with better quality livestock, will order some for you. Why take the chance of introducing ich into your system if your experience with that LFS