Cannot "arrest" something that's not a natural person, but yes, they could absolutely seize a bot under a number of civil forfeiture laws, or likely as evidence. The burden would be on the owner to sue to get it back.
The point is what a designation is for; in the case of an arrest vs detention or seizure for natural persons, it's usually an elaborate shell game around when various search doctrines or other restraints on police behavior kick in. In the case of property, the only point is to grab your stuff; the circumstances surrounding it don't particularly matter because they can always decide later under one doctrine or another that they're entitled to keep it.