I posted this problem in the spoilers section but didn't get too many responses so apologies for reposting but this is doing my nut now... Cait has vanished and I have no idea where she's gone... I've been looking online for solutions but not found anything to help... I sent her to Abernathy Farm as Sanctuary was at max capacity (before I knew about taking chems to increase max charisma) and she never returned... I have waited for a good in game week... maybe even longer... I have kept going back to the Combat Zone and even the last place I dismissed her... I've checked Red Rocket and I just don't know... I have heard that some companions walk slow but I dismissed Dogmeat from the heart of Boston and he was there it took me the time to fast travel there...

Ya each time you dismiss a companion you need to pray that you will ever see them again and they won't get stuck on anything in the wilderness for the rest of eternity. They really need map markers for companions, just tiny ones that aren't clickable would be enough.

I eventually found Strong who I lost, he was just walking into a tree trying to go to red rocket... I was like "Strong you are not that strong, go around the tree next time"

As tedious as it is, I always take my Companion with me to the place I'm going to 'send' them so that they don't actually have to GO anywhere.