611.2b. Some continuous effects generated by the resolution of a spell or ability have durations worded "for as long as . . . ." If the "for as long as" duration never starts, or it ends before the moment the effect would first be applied, the effect does nothing. It doesn't start and immediately stop again, and it doesn't last forever.
Let's say I cast and resolve Master Thief, and his triggered ability trigger targeting Squee's Toy (a metaphysical artifact). In response, one of my opponents takes control of Master Thief (with, say, Dominate). After they gain control of it, I also cast and resolve Dominate gaining control back. This is all before his triggered ability resolves.
Now, I know that the intent is that I will NOT gain control of the artifact, but the rule doesn't actually say that, nor does it provide a way for abilities to know whether or not the "as long as" clause has become false since they have been put onto the stack. At the point the ability triggered, I control master thief. At the point it resolves, I still control master thief.
In other words, effects shouldn't begin applying before they resolve, which is what's happening here.