It was in the root directory, and it was on a freshly formatted Cfexpress card...which is what I shoot on 99% of the time because of the transfer speeds...I had to go rummaging around to find an old sd card to load the firmware onto. Funny thing, the one I found was apparently the one I used for the previous firmware update, as it still had the EOSR5130.FIR file loaded...so I guess I need to keep that card handy.
