I had that happen once, but it was the other way around. I worked at a call center, and just as I was about to log off the phone to take a potty break, my phone rang. Figuring I could hold it for a minute, I answered.
This person asked every question under the sun. I was on the phone with her for 15 minutes with no end in sight. So, on the next question, I told her I didn't know and would have to check, would she mind holding a minute while I found out? She said sure! So I put her on hold, and ran to the bathroom!!! I was back in about 2 minutes so she wasn't even holding that long. The call took another 15 minutes, so I'm glad I did what I did, I would have exploded otherwise!