As I could just discover, there is a trading post bug regarding the trading history.
The bug prevents you from seeing buy offers of a certain age if you place a rather large amount of buy offers quickly.
Case: I just placed buy offers for approx. 50.000 crafting materials. As a result, I can’t see any buy offers that are now older than 15min, even if I saw them an hour ago. Adjusting the selection or sort order changes nothing. The items from the buy offers don’t appear. This prevents players from cancelling their buy orders and can become rather expensive pretty quick.
Sweet irony has it, that I just wanted to delete some weapon skin orders, which have now successfully been fulfilled.
A bug report with screenshots has been filed.
If you need further info, please do not hesitate to contact me in-game.