Over the holidays we had an accidental deletion of every image on one of our phones (a Nokia N90, Symbian OS device.) Mild panic was quickly replaced with a gentle pondering on the difference between what a normal person would do in this situation vs. what a geek would do. The geek process goes something like this:
Either shut the phone down and pull the card, or use the super-secret combo hidden within the profile-switching shortcut to have the phone un-mount the card.
I've needed a reason to buy one of these for a long time. Good thing I had a gift card left from the holidays. I went with a Dynex gazillion-to-one card reader, not for it's technical superiority, but because it was the only thing the shop nearby had.
Mine happens to run Ubuntu at the moment, but the results will likely be similar on other distros.
Testdisk "was primarily designed to help recover lost data storage partitions..." and includes a utility called "PhotoRec", which is what you want.
PhotoRec is a data recovery tool designed specifically for recovering files from digital camera media. It supports a number of file-system formats, including the FAT format that Symbian OS uses on it's memory cards. PhotoRec is a text-based, terminal application, but it does the job perfectly.
Select the mounted memory card from the list of drives (which should be easy to spot given how small memory cards are relative to modern hard drives) and send it scanning. PhotoRec can be told to look for specific file types (you want JPG's, in this case) but by default it will look for just about any media file format that you're likely to have on your phone. Files will be recovered and written to a local directory.
PhotoRec isn't going to restore the images to the memory card's file system such that the phone can see them again, but you'll have the pictures on your Linux box now, and can copy them back over if you choose to. The naming scheme will be different, but that's an acceptable compromise.