The whole claim is pretty 'convenient', presents a role we're unlikely to have - watchers being rare even in big games but well known - thus making it a pretty safe claim and matching your HC.

The problem here is you suspected Taiga, now a watcher sees who direct night actions at a player, not what they do. It's usefulness when targeted at a suspected scummer is pretty small then. People rarely NK good scapegoats, were I scum Yuna and Taiga and anyone who didn't vote for Rana yesterday would be at the bottom of my NK list barring some strong indicator they were a town power role. If they're a known suspect, it's handy from a watcher POV for trying to figure out who the cop is, for a known probable NK target, for finding out who the doc is. So pretty much your only logical reason for checking out someone you suspect isn't because you suspect them, it's because you think others suspect them and you're hoping to be able to ID an investigator role. A townie trying to find out covertly who the cop is isn't a bad thing but that's a tough maneuver in terms of the odds for minimal gain. Knowing who the cop is for a townie really only matters in event of a double-claim, itself a rare thing that usually ends badly for the fake claimant.

Now, we're way outside of plausibility here, because one is weighing all these stacking improbabilities against the flat out one of watching someone who'd be a good Night target or even a random player and finding out who struck. Just to review this one:

1) I will target someone I think is a scummer (call it 50/50 and that generous)
2) I will assume, in spite of their being contradictory evidence (Rana, a known scummer, voting for Taiga) that other people suspect Taiga enough to investigate. (Maybe 1 in 4)
3) That another scummer, not Taiga (in spite of one already being dead, 50/50 there's another) will false claim as cop (1 in 4 at best).
4) That your announcing yourself as a watcher during a double-cop-claim would make a difference when in all probability it would get you murdered as an asusmed co-conspirator. Call it 50/50 though)

So .5x.25x.5x.25x.5 or 1 in 128, less than 1%... not really a good action plan. Other scenarios are actually worse, like trying to ID an RBer, who could only be acting on a probable scummer if they were a Town Rber - very rare - or if the person wasn't a scummer.

Really just going over that because the 'I hoped to find the cop' is the only sane reason to go watching a player you suspect.

So our options here are that you're lying or that you seriously blundered with your Night Action strategy.
Vote: Stephen