It was probably me (as in I know I rode homeTuesday last week and might have been in my pirate top) , although I didn't hear you, sorry IS. I get to ride in while the kids are off school, so I usually try & take a detour over a hill or two on my way home. Some company for at least part of that would be a welcome change!.
O&G = oil & gas, FT.
I'll be out for a run this lunchtime, if any of the apparent multitude of pirates on site spot a balding bloke in a red top on Springfield Drive shortly after 12 that'll be me.
I had a similar problem a while ago, and it turned out that the problem was a stiff link in the chain that would cause it to jump at the back, but it only happened when I used the large chainring, probably because when I used the small ring the sharper turns through the rear mech sorted out the stiff link.
Otherwise, if it only happens when you're working hard, it might be that the frame is flexing and the front mech is pushing the chain off.