Dave,
Yup... not sure why they're there... and I too had a few there when I moved the bottom board down for the spring. Last night they grew in size and today back to a couple hundred.
Whatever their reason(s) for being there, I am not going to tell them to move. I don't think that they 'can't find' the entrance to the hive given that they typically travel miles and find food and report back on its whereabouts.
Leaving well enough alone. And ps. They've been doing fine for 6 weeks and have built 11 combs and growing. Something is working

and I think it's that I have left them alone.