A few weeks ago I got a phone call inviting me to a campus interview / job talk. I was really not expecting it and answered the call without even thinking it might be about an interview (caller ID said a different city than the one where the school is). Anyway, I was kind of caught off guard and while I think I did express enthusiasm and excitement about receiving the invitation, I have since read some advice stating that one is supposed to treat these phone conversations almost like a mini-interview, ask questions about the school, etc. I did not do that (I treated it merely as an invitation, some logistics were discussed, I said thanks and that I was very excited to visit the school — that's about it, it lasted maybe 10 minutes). And now I'm wondering whether I've already blown this by nature of that phone call with the chair. Of course, I will talk to this person much more extensively when I actually visit in person next week, but I am really hoping that I'm not heading into the visit at a disadvantage based on my phone performance. Any thoughts?
My feeling about this is that if they don't schedule a phone interview but instead just call you out of the blue to schedule an on-campus interview, then the phone call is not an interview. If they wanted you to treat it as an interview then they would say so. They have already decided that they are invested enough in you to go to the expense of flying you out to their city, so I don't think your brief interaction over the phone is going to sway them in one direction or the other, unless you came off as arrogant or uninterested in the position. Their impressions of you as a candidate will be mainly derived from their personal interactions with you when you actually visit.
During my job search year, I had a phone interview that I somehow didn't correctly note in my day planner. The search committee called my cellphone when I was in my office (buried in an building with poor reception). I had completely forgotten about the interview, answered the call, and hurried right in front of one a faculty member's office to sit in a window to try to keep a good connection. It wasn't a pretty interview, but I got an on-campus invite. So, you should be just fine - especially as this does not seem like a standard phone interview.