This has since been fixed. This PSA was from roughly November 22, 2016 to early morning November 23, 2016.

Public Service Announcement – We are getting a lot of reports of items disappearing when dropped on the ground. Do not drop anything that you care about!

This can be reproduced by dropping an item and doing a force sync. Usually after a few tries the item will disappear.

We have also heard reports of problems with linking and fielding. A link can be made, the AP is awarded, but doesn’t show up for anyone else. Force sync and it disappears, but your key is also gone.

Also seeing a lot more ghosted links and crossed links.

UPDATE 8:49pm ET – Looks like dropped items that were lost are appearing in the positions that they were dropped (within the past half hour)!

UPDATE 2:26am ET – An update has been published by Niantic saying the issue has been resolved.