Lexar jumpdrive firefly 16GB I've deleted all files off of this thumb drive, it is now empty, however, all the memory is taken still. I can't put new things on the thumbdrive as a result.

Yes, it is possible to recover your files from lexar jumpdrive. see this step by step guide

Recover deleted formatted files from Lexar usb drive

you can use it to undelete your files from lexar jumpdrive.

First of all try a data recovery program such as Wondershare Data Recovery to get the deleted files back. Get the program here,

Data Recovery Windows (for Windows OS)
Data Recovery Mac (for Apple Mac OS)

Then format the pen drive from Disk Management if you are running Windows.

Remember - Do NOT try & write anything back to your pen drive until you can recover your data safely!