I had a phone interview via an intro, then came into the office to meet with the CTO. Everything went well, and I walked out of the office with pseudo-offer. I got a real offer via email, then we proceeded to start negotiating. As we were negotiating, the CTO dropped off the map and stopped answering emails! I spent a large amount of time interviewing with them, so to be ghosted was pretty unexpected and unprofessional, especially since we were already negotiating.