Hey villersb, we have successfully done this with our android tablets. Here is the process that we used.
1. Grab the geodatabase from the program files on the android tablet. 2. Next run the export xml workspace tool (Collector geodatabase) and the import xml workspace (new geodatabase). 3. Uploaded layer to AGO, and all data and attachments should be accounted for.
Let me know if you have any questions. Now we just need the process for ios devices.:)
Still looking for a solution to this, has anyone figured out how to recover data from a collector device when it fails on synch? How does this .geodatabase file translate to XML?