That sounds like one for Sherlock Holmes. Welcome to the forum, Janet.

We lost both our colonies two years ago - I mean they just died in situ in the cold snap even though there were still stocks of honey that we left for them. Both hives were repopulated by swarms in the summer. This year, it looks like at least one may have survived although we have not gone in yet.

But if there are no bodies, Janet, then they must have departed. Just my opinion as i am no expert.

You don't have to do anything if you have a hive. They will just arrive if they choose to. It's pure luck but a hive of some sort increases your chances as it provides a ready made home and may be found by the scouts who are sent to find a location for a new swarm. We think our both ours came from a neighbour . . but we did not double check with him!

We got a swarm one year from a local bee expert who had left a simple "nuc" out in his yard, not with any intention, but a swarm just landed in it. A "nuc" is a mini-hive used for transporting colonies or housing them temporarily.

If you join your local branch of the beekeeping association (I can't recall its name off the top of my head) and undergo their training course, then you will be on the list to be given a swarm. Our first colony came that way, from somebody who was giving up beekeeping