I hired Erik the slayer, gave him new armor and weapons and went to a nummer of locations Before he disappeared and i could not find him. I waited for 5 days, did not help. But then I found him in Rorikstead again, but witout the armor and things I gave him. I had to "rehire" him but then he sain that "it looks like you already got someone.." althoug I didnt. Someone know why? Even lydia says the same thing.
I have had a lot of difficulty with Erik disappearing after quests make him go away. I've found asking to trade with him will make the items reappear (if you can manage to work around him not following you). I also know that some people have randomly encountered their dismissed followers in the wild. If you can remember where you were when you dismissed your last follower (not Erik), follow the route from there to that follower's home. You will encounter a metric ton of deer, saber cats, wolves, and random enemies, but there is a chance the follower you can't get rid of is wandering out there, lost and alone and taking up a precious spot on your team. Just a chance, mind, but this is the only solution I've come across in my MANY "quests to find where the hell Erik went to" that relates to your problem. IF your problem is that you already have a follower lost out there, there is also a possibility that you accidentally interrupted that follower's route home by walking to near them and triggering a dialogue. In this case (this has happened to me), that follower will be where you interrupted them, loyally waiting for your return.