Hi, in most cases this can be resolved and your trade either found or checked through our support system, if we determine you have been API scammed please follow these steps below to secure your account.
It seems that you have been API Scammed. Sadly we are unable to help you in this situation as we didn't receive the skins that you deposited. Here are the steps to fix this problem, and stop this happening for your future trades.
Please go to https://steamcommunity.com/dev/apikey and click the click the "Revoke My Steam Web API Key" as shown in the picture below.
2. Once you have clicked this, you will see a box that says "Revoking your Steam Web API Key will stop any apps that use this key from working. It cannot be undone. Are you sure you want to do this?". Please click the OK, this will then revoke the API key. This is not needed by us and you should not be giving this out to any site. The example of what you will see is shown below.
3. Once you have successfully revoked your API key, you should see the page looking like the image below. This means you were successful in revoking the key and no application or website will be able to use this to hijack your trades between us or any other party. We do suggest changing your password that is attached to the account and resetting your 2FA if possible just to make sure.
You can see how to reset your 2FA and any other queries in the steam FAQ.