Due to my own ignorance I deleted the accompanying .thm files that came along with the .mov files from the Canon digicam. It would have saved a lot of trouble to have checked what they really were before deciding to do away with them.
Based on what I gathered, .thm files are actually thumbnail-sized .jpegs which include some metadata pertaining to the file they came with. For videos this would mean they act as preview image as well as provide other information such as duration and time of the video, of course, the files should have the same filename except for the file extension. With the files gone, it will be impossible to play the videos in the digicam or even with the Canon Zoombrowser EX application (ToT).
Some people have used the .thm files from other videos, but since the metadata don't match, there is a chance that video playback will not function properly such as the video ending sooner than the actual length if the information is shorter than the actual video. After a while of searching, I stumbled upon a forum thread where a user named halligang provided his self-made application to recreate the .thm files which you can check here and here for the beta2 version. The app will allow users to extract still images and capture these as .thm files. So far they allow the Zoombrowser to preview the files, though it seems the camera still can't recognize both files as they are not being displayed when browsing the SD card contents (still trying to work this out).