Fascinating, how like the last 10 posts / posters are misinterpreting the context and going completely offtopic into something irrelevant to the OP's problem - only because of reckless reading that made them slip into a backup-tribute coma. He got 99 problems but a failing hard drive ain't one. He only wants to undelete / recover a deleted file. Therefore, he does not need to maniacally image his drive, unless he feels uncomfortable about somehow pressing the wrong set of keys - which is pretty hard to fluff up anyway, as testdisk presents you with a descriptive dialog and a warning, specifically for that exact thing (saving to a different storage). Lecturing about the importance of cloning is one thing, understanding the issue at hand and presenting a rational solution - is another. Imagine the redundancy, if he only needs to locate a single deleted file and is going to image a 2TB drive, just for that. Can speculate, that he might simultaneously have a failing hard drive, but what are the odds of that in this particular case? Pretty low. If it was really in such a bad shape - it would die regardless when being imaged or when testdisk would've had it's way with it: you either get an incomplete image or an array of recovered files. One is not much better than the other.

Also, it's not really testdisk, but photorec for the needed functionality.

(emphasis mine)

When dealing with data belonging to someone who is paying you and trusting their data to you, which is more important? Absolute safety, or saving a few minutes?