You're pretty good technically speaking with your Pika. There were 2 glaring things I kinda want to point out that got you beat this match though. The main one is that QTP won this one largely because he waited for you to throw out a laggy attack, then grabbed you and comboed you a couple times before you died. Also, look for more grab opportunities while you're playing his sheik. I saw quite a bit that you could've taken advantage of whenever he returned to the stage.
Also, another one is a general tip vs Sheik that you didn't really take advantage of. QTP should've lost more stocks than he did in my opinion, and it's the main up pikachu has in this matchup is your edgeguard game vs sheik. As everyone notices, Sheik's return is broken in ways, but she suffers from the same weakness pika has, and its that she's super vulnerable if she has to land on the stage. Main difference is that sheik has to land somewhere very close to the edge, otherwise she loses the preferable option of grabbing the ledge and slapping you for being near it. Whenever you force sheik to land on the stage, you need to NOT hit her with a weak attack, but either ledge hop and neutral air her on the opposite side so that she'll fly off the stage again, or tap the control stick forward, so you roll onto the edge, and either f-smash/usmash/ or throw her, percentage determining what you do.
But yeah, in general, trying to fsmash sheik as she's returning is a bad idea, cause she can ledgehop and smack you right through it.
That's just what I noticed. I could be completely off, and someone else might notice something completely different, that's my opinion on that match though. =].