Bees nesting in house walls has driven me crazy for half of my life. Every spring, I will get phone calls from people asking why do bees keep coming into my house?
The first telltale sign that there are bees in your walls will be that they will be flying consistently in and out of a hole, or gap. There will be at least a few bees per minute when it is warm.
Bees are cavity-nesting animals. If you fill the cavity, they cannot move into it. I find polyurethane expander foam is an excellent way of preventing them from returning.
If a beehive is not managed properly it will produce swarms. Swarms move around looking for a specific type of place to build a nest. Normally a swarm will move into a wall around midday.