I guess there is a chance that is possible if you have a alot of storage, but if your only using 1TB im doubting that you would have 500gigs of garbage if your node was online. Unless of course data in buckets have a time limit and they all get wiped, after so many days.
This is an old node since last summer and yes, back in the early alpha days I think a bunch of files were never deleted and built up on the drive. more than 6TB space. There was a question about deleted file cleanup back in the fall and STORJ said to wait they were working on it and they would take care of it in the future, thus garbage collection. So, yea, 6 months + of garbage collection and it seems to be working for all those lost files on my drive.