If you don't reuse that password anymore, does it matter tho. Some services might use older hashing for older passwords without updating the hash algorithm. But I don't know what is the case here.
I would hope that a system competent enough to migrate to bcrypt would also be competent enough to rehash the entire database as well. Logins check bcrypt(oldHash(pw)); if it matters they can be updated to bcrypt(pw). Of course, "Hope is not a strategy".
brypt passwords are very slow to crack.