No longer able to see photos I attach in mail

I am a pro photographer and attach images in mac mail all the time. about 3 days ago I could not see a photo if I attached it. "missing plug in" appears instead. sent test email to a fellow shooter and he received the image. Not sure if something got thrown away by mistake. I empty my trash daily. went to Time Machine and tried to find the trash folder for that date but could not locate it. No idea what it would be called. I am working in Mac OSX 10.5.8. thanks!