Mine would do that, totally unrelated to being in heat though (cuz my boys did it too lol). They'd back themselves up in a corner and let it go... some was bound to get on the wall haha. I solved the issue by putting up a clear shower curtain behind the cage. They could pee on that all they want, I could just wipe it off and not worry.... don't really want it on the wall though.
I have heard the same thing as Kady, about cleaning TOO much. I've never been able to test it, because I am not one to obsessively clean anything In theory it makes sense though.
I thought Yesterdays News worked really well, so I'd definitely give it a shot; doesn't sound like you have anything to lose!