C182 pilot reported they were temporarily NORDO when they selected the wrong radio on their audio panel and flew below the ATC Minimum vectoring Altitude.

Narrative

Was given vector of 030 while still on initial climb; having departed ZZZ. After 8 or 9 minutes I clearly saw that I was heading towards the hills and queried to ask for a new vector. The reply was that I was on the wrong frequency. The frequency I was on was still in primary on Com1 but the transmit flop on the audio panel was now on Com2. In retrospect; while attempting to select monitor Com2; I must have accidentally pushed the select (com/xmit) button; which essentially eliminated COM1. When I called in later and explained what happened; the controller told me that it became a deviation because I continued east into an area where the minimum IFR altitude was 5000 & I was still at 4000. I could still see and there was no terrain CFIT hazard.I am sorry this happened but glad also because from now on I will strive to deliberately ensure that I immediately communicate anytime right after making any COM panel changes. Whether I fat-fingered my selection or whether it was turbulence induced I'm uncertain but making a habit of checking COMs after any changes will surely help in early detection and correction.