Building material stuck under new building

[warmer]

I demolished a building and replaced it with another. I thought my engineers would use the materials closest to the site (on the ground from the demolished building) but they left some and now they are stuck underneath.

This is causing my engineers to get stuck trying to get to them when I place a new structure with no success.

Will these eventually despawn?

[Shidan]

Not if you stay nearby. If you take all your characters away they will despawn as soon as the area is unloaded, other than that or importing they will stick around forever.

[warmer]

That makes good sense. Thank you for explaining that. I'll need to take the whole gang out for a field trip then. My engineers are at random getting randomly glued to the side of the building until I discover them.