I mean, who actually knows what happens if you don't live anywhere?
This speculation would require you to hack the game so that the Spewpa came from nowhere and hack your 3ds that it came from nowhere.
There is no telling what would happen then; but even so, does the game crash? Since location is part of it's code, It may (this is also quite speculative) do one of the following instead: evolve into a random form; or, evolve into one of the event forms (Poke Ball and Fancy) instead.
Again, we really don't know and need to hack to find out :P