X100vi user here, and I faced the same problem too. I did not have RAW switched on, but I chose FINE/HEIF and got the "no image in the memory card" message. After reading the posts here, I change to FINE/JPEG and problem solved. Thanks for the posts.

Yes, I managed to replicate the issue - took a photo, numbered DSCF1232. Copied to the SSD drive, where is appears as DSCF1233. Take a second photo on the camera - this is DSCF1234.

Interesting - sounds like you've found the reason for the discrepancy - I guess the SSD drive option is new to FujiFilm and they don't have it quite right yet

I kept the same two cards in the same slots throughout the trip - I didn't touch them at all. However, I didn't check that card #2 had an exact copy of the files on card #1, and I've now reformatted both cards. But recovery software shows the expected number of deleted files with the correct capture date & time on both cards. Note that each evening I copied the contents of card #1 onto an SSD drive attached by USB-C cable, using the copy function in the camera software. There's no option to copy only new files, so each day the camera copies the entire card's images onto the SSD drive. You would hope that it would overwrite the existing files, but this is where it gets bizarre. The SD cards each have 313 JPGs and 313 RAF files; however, the SSD drive has a total of 644 files of each type - some of these images are duplicated twice or more, with different file numbers - and the file numbering between SD card and SSD drive don't match at all - in fact, there are no file numbers in common between the two media. It seems likely that the problem is a bug on the Copy function in the Playback menu - as far as I can tell, the copied files on the SSD drive are given new numbers by the camera, as if they were new images, sequential with the existing images on the SD card. So, if the SD card has images 0001 through 0020, these are copied to the SSD drive as images numbered 0021 through 0040 - and the next photo taken by the camera is given the number 0041. This is a bit of a mess and needs sorting out. Do Fuji follow this forum closely or should I contact them directly? Incidentally, I would much prefer it if the Copy function only transferred images not already present on the SSD drive. It would also be nice to have the option to have the camera save photos in subfolders corresponding to the capture date, eg. F:\DCIM\100_FUJI\2025-05-22 and F:\DCIM\100_FUJI\2025-05-23 etc., as my Pentax K-1 does.

Did you change the cards between days? did you take out the cards between days? did you use the same cards for the entire trip (and both cards in the same slot i.e. not switch cards between slots)? Are both raw and jpeg images on both cards for all images? (Not that I have an answer but looking for something that changed between days)