A player can be traded, bought out, and then re-sign with their original team (Orpik did this with Washington). A player can even be bought out by their team and then re-sign with that same team (Calgary did this with Michael Stone). However, the key is that this cannot be pre-arranged or agreed to. If there was any evidence that the teams or team and player agreed to the arrangement in advance, then it would not be allowed.  So assuming Yamamoto and the Oilers didn't pre-arrange it, yes, after Detroit bought him out he could have signed with Edmonton.