You seem to have multiple things going on.
First, it appeays that you are in the habit of moving your SD card from device to device.
This is a bad habit.
Get a separate card for each device, and leave it there.
Second, strange and sometimes bad things happen during the updating of apps.
Generally, I also update if one is available, but if the update does not affect my device or has no interest to me (always check the changelog) then I usually will not take the update.
There is an old saying- that you don't update software that is working properly.
Most of the problems I have ever had with software came right after...
you guessed it...
an update.
Now, this may not even be your issue at all.
How did you purchase your SD card?
Was it a name brand from a brick and morter store?
Or was is an 'el cheapo deluxe' in a twin pack that was on sale online?
There are many, many fake cards out there, that are sold as having much more memory than they really do.
They will fill up way before expected, and then crash or lose data in other ways.
For files/folders to just up and vanish off of internal memory is quite a different thing.
Unless something is wrong with the device, you did a factory reset, or deleted the files yourself, then it is exceedingly rare to just lose data.
That is why I suggested the other gallery.
Not only because it is a superior app, but because it may see these files that you cannot otherwise find with the apps you are already using.
Another app you could try is by the same developer, Simple File Manager.
Use the three dot menu in the upper right, then select 'settings'.
Then select 'show hidden files'.
Simple File Manager (A simple file manager for browsing and editing files and directories.) -
https://f-droid.org/packages/com.simplemobiletools.filemanager.pro
The idea here is that you may have (hopefully) inadvertently hidden these media from the apps that you have been using, and that these apps will still see the files.
The other reason for you to try these apps is so that it is easier for me to help you, as I (and others on this forum) use the same apps myself- and am completely unfamiliar with your apps (or device for that matter).
This would put us on more common ground.