After lengthy technical problems with steam, items were returned to inventory. They also now drop out in the game and can be bought on the trading platform.
Why are items missing?
On September 16, messages about unsuccessful requests from the game client to the steam inventory service were poured into the developer console. As it turned out, the inventory service was disabled ... I enabled it again through the developer site, but after 2 days we started receiving messages that all items were missing from the inventory.
After 2 requests to the steam support service, which remained unanswered, I once again went to the developer site and carefully looked through all the settings and it turned out that steam automatically switched the inventory to hidden mode. At what point this happened is not clear.
At the moment, we still have not received a response to any of the last two requests from steam, although now they are no longer needed. Let's pray for steam and its wonderful staff.