I have been using the steam web APIs for some projects.

Recently, a Treasure key I traded for suddenly became "Not tradable" on my steam community profile(http://steamcommunity.com/profiles/id/inventory). It remains tradable in my Dota 2 inventory.

Upon further investigation, the Json object derived from the API response contained an item that had all the details of a Treasure key but the ID of a non tradable item.

This could really mess up websites/projects that depend on the APIs to function. This bug just surfaced Today.