May i know what is the version of the Lightroom you are using.
Try creating a new catalog and try the same in that as well..
I saw something similar but in my case the photos did get moved. But LR reported that many thousands could not be moved. It's a very spooky message. I'm using the latest version of CC. I'll have to really poke around the library and make sure everything is still intact.
Please help. During moving photos from one folder to another by simple "drag and drop" some of them get error message "File could not be moved to the selected destination" and files cannot be located anymore. They are just gone and cannot be found even in the trash bean. After getting this error I have experimented for a while and found that almost every 5th relocation of photos between folders has this bug. Similar problem appears during deleting rejected files - during the process the fault comes telling that one or two files cannot be deleted due to the same problem. Although it is not critical for later case as I want to delete them anyway but it looks like similar issue. So now I have to stop using the Move File option within Lightroom otherwise I keep losing my files.
Restore the photos from your backups.
In the future, to move photos, use your operating system and reconnect in Lightroom, see the section entitled "Updating Folder Location" in this document: Adobe Lightroom - Find moved or missing files and folders; or better yet, develop a workflow that doesn't require photos to be moved from folder to folder.
There seems to be a rare bug that Adobe claims they cannot find regarding photos disappearing when moved in Lightroom. Please read: Transferring photos to an external hard drive, photos lost. If you'd like to complain to Adobe, do so here: Lightroom: Moving files, resulted in deleting the files