So basically I went to the Red Rocket Truck Stop with piper to build on the settlement. I got out of my power armour and entered the workshop, while I was using the workshop Piper randomly entered my power armour. She kept getting in my way when I was building so I dismissed her to the Red Rocket Truck Stop (where she already was). When I finished building I realised she was gone with my power armour lol.

I have tried waiting for over a week and ringing the bell, I also went to her house, the mayors office and nicks office but she is nowhere to be found. is there anyway to fix this?

She's gone!
She went off kill some raiders

She was following you around just to get that power armor from you. Sneaky little girl.

lol, I decided to try sending other companions to the same place. I sent Nick and Dog Meat and they both showed up, but Piper is still missing.

Take out the core from the power armor then they can't steal it

As for your fix, look at your quests and see if she has an active one. she is probably waiting for you somewhere.

ok will give it a try thank you