Adjustment of Status - I-485

Hello everyone. My wife and I have recently received an informed delivery update from the post office showing us that a piece of USCIS mail is on the way. At this point, we are not waiting on anything else but an interview notice. Nothing was updated on the USCIS system (as it often fails to) and we have a feeling that this might be the interview notice. However, that piece of mail never reached our mailbox and after speaking to the post office they said that it was probably lost. We went to the USCIS field office today to see if we could find out what was sent to us and the date if it was an interview office. They said we have to call USCIS and get an appointment. We called and spoke to a level 2 officer who was extremely rude. She said that she didn't see an update in the system and cannot schedule us an appointment to speak to someone. If it was an interview notice, she said that we have to miss the interview and if we miss it, they can reschedule it later. wtf!!! That's over a month added onto our wait time, if we're lucky. We called again to try to reach a nicer agent, and another guy listened and told us that he also doesn't see an update in the system, but based on his "professional opinion" he thinks it was probably a notice of fingerprints being applied to my case. I've already received my combo card, why would I get fingerprint being applied notice at this point? Has anyone else received such a piece of mail before? This is so frustrating.

I don't know what to do at this point and don't want to miss my interview if that is what was sent to me.