I think your best bet here is to give Heartland Customer Service a call in the morning at 877-262-8032. Give them your VIN and ask them your questions. Circle back here to let this group know what you found.
I reached a very helpful chap at Heartland Customer Service named Alan.
He found our trailer registration and then messaged the engineer in charge of that trailer line with my inquiry.
I just received a reply.
Apparently this model (Edge) does not have any wall studs. It is what they call a 'perimeter framed laminated wall' which I think means that the wall is made from a strong foam core with the fiberglass exterior and wood interior glued on.
The only framing is aluminum studs or beams around the outer edges of the wall, like a frame.
Now I need to decide on an appropriate method to re-install the awning uprights to the wall.
I will first fill the old holes with a sealant and ensure the wall is flat and clean.
I intend to glue the uprights in place using an adhesive or 2-sided tape and then use new fasteners in new locations on the uprights.
Any suggestions on an appropriate adhesive or tape and on what the best fastener would be?