iPhone 5's default earphones' controls suddenly stopped working.

Last night, I was on my way home while listening to music from iPhone. My partner called me and I was able to answer her using the headset controls. After the call I went back to listening to music.

I pushed the "pause" button as I was trying to talk to my seatmate but I wasn't able to turn the music back on when I tried. My seatmate had the same iPhone and I tried to use my earphones/headset to her phone, I was surprised to know that it wasn't the phone.

Music constantly runs through the wire with best quality. But not the controls.

Can someone help me? I don't want to buy a new one.

Thanks,

Adrian