My Internet USB dongle is currently broken, so I cannot connect to the Internet. However, satisfactory and its saves are still here. I decided I could continue anyway, and it prompted me to go into offline mode when I loaded the save. However, once I joined in, I realized I loaded in at the Hub (I had not saved there) and all of my inventory items were gone.
Upon exiting and reopening, it did the same thing, and I also noticed that it didn't show my username, just a number. After messing around for a while and then saving and quitting, I rejoined to see that it had done it again. However, I soon noticed that my playermodel from before was still where I had left. Every time I join into my own save I'm a new player, unable to access my previous inventory and cluttering my factory with clones of myself that I will not be able to get rid of as far as I know.