Not too sure what type of bumblebee, they were very light orange, nearly yellow With black stripe(s) - Also they were a quite small type.
My knowledge of bumble bees isn't very extensive, I only know the basics.
SDQ: The queens leave the nests late in the season & hibernate over winter under stones/sheds/debris. They emerge again in spring & find themselves a new place to nest & lay their eggs, so yes they nest in a different place every year. (they only live for about a year so the queen will die at the end of the season)
Cock robins choose a few nesting sites & fill them with leaves, the hen robin will then choose which site it wants & they will then build their nest. The bee probably laid its eggs in the pile of leaves before the robins built their nest.
Normally when we get a bumble bee nest in the garden, they are the common type, & either nest in a large pile of stones/slabs near my composters, or on the ground in a small wooded area. If on the ground, all that can be seen is a small pile of leaves. I have tried to encourage them with upturned clay plantpots full of leaves for them to nest in, but they prefer to build their own nests.