That happened the other day. My friend and I were doing a 30 miler. We were passing a city park and SHE said "do you need it?" and I did not. Well, five miles later I did. Fairly open area but the trail was under a huge power line corridor. I found a tower I liked but my friend was not amused! Of course, guys are slightly better equipped at making due. She had to wait till the next official bathroom!