C25K app glitchy?

lorrpb

I used c25k app for first time today (during a walk as I still have chest congestion). After starting the app, I pushed the lock button on my iPhone 4s before putting the phone in my holder. I do this do nothing gets pressed accidentally. But then I got no prompts from the app, although I could hear my music. Then I went back into the app & put it into the holder without locking the screen & it ran fine. Is this how it is or is there a workaround? Thx.