In order to get Bruce back, he'll need to stay in the friend's village until the village he came from cycles through 16 more villagers--that can take a very long time (or it can take a few hours if you TT and don't care who moves in and out). There is no known way to get a villager that moved back until the game forgets you had that villager. 16 villagers are reportedly stored in memory. Once four villagers move out of your town, those relocated villagers (whether they went to other towns or just left into the digital void) will appear on Main Street. They game has to cycle the villager through Main Street, having other villagers replace them. Once you've cycled through 16 villagers that relocated since the TT accident, you can have your original villager back.
That's how I understand it, and from what I've read there are no exceptions. There is a rumor that you can have the same villager (meanining the same one you traded away--not another instance of the same villager) move back into your town without having to wait for the villager to cycle through Main Street, but that is not true.