I'm having the same issue. I patched, got into the game, I chopped down the closest burr to the tree, as I was in the process of building up my base. I noticed after a couple days the burr did not respawn, so I went across the yard to farm some... lo and behold, as I'm looking atop the perch of the porch chair, there is literally no burr in the yard. I've gone to all my usual spots - nothing.
I find it odd that there was burr when I logged in, but as a couple days passed I suppose it all cleared itself from the yard with no warning. This is a big issue for me because I'm at the point where I'm building with finer materials, and the only thing left I need is to install the floors. I need burr for that so I'm kind of at a big loss here.