It is easy for inexperienced analysts to confuse crap on a 'clean' slide for nefarious objects
For reference: these are what blank slides look like at 400x magnification before and after cleaning. Obviously all slides are different and may have different manufacturing processes. Below is what we found on ours.
AFTER WIPING WITH ANTISTATIC (DRY) KIMWIPES
PIECE OF TORN KIMWIPE TISSUE FOR REFERENCE