Interesting bug. Go to your Library window, find that file, hover your cursor over the file. Is the file size & details the new or old? Did you refresh your Library or restart LW after re-adding the file? (turn on extended tooltips .. ie: right-click the heading bar of the library & choose to show ext. tooltips; example of how to do this on the download window: http://www.gnutellaforums.com/335192-post4.html; you can turn on ext. tooltips on all windows including monitor window)

Which version of LW are you using?

I am aware of a similar bug with LW. At least for descriptions & also for id3 tags; showing incorrect information.
(On that topic, my LW thinks an mp4 (H.264) video is an audio file when trying to describe it, despite mp4 is not listed in the audio extensions, but is in the video extensions of sharing options. I had to custom describe it adding a video description under advanced describe options.)

Your bug would be worth reporting to LW. Create a new issue at this site: https://www.limewire.org/jira/browse/LWC (you will need to register there)