Maybe its defaulting to your Documents folder on your OS hard drive. You could also this: when the reconnect media window pops up, try hitting the search tab. This will scan your drives for the file name.
A good habit to get into is keeping your projects organized. Your capture scratch is only for captured media. Anything else you want to import should come from your project folder. Some people keep the Capture Scratch and FCP cache files on a separate drive from the project files. It should always be on a separate drive from the OS.
With my system being screaming fast with a RAID 0, my project files, capture scratch and cache files are all on the same RAID setup. That gets backed up to a FW800 drive. This frees up the OS drives to do there computing thang.
I create a Project folder. In there place your FCP project file. Then create a Media folder. In there place your Images, non-captured video, audio files, motion files or anything else.
I know this was long but when I started out, someone else gave me this advice and its saved me tons of time. Hope it helps.
OS 10.5.5, Mac Pro 2 x 3 ghz quad-core intel xenon, 9 gb ram, with BM Intensity Pro card