Thanks guys, thanks for jinxing me... I hadn't lost a hitch pin ever and I have owned my tractor for now on 13 yrs. Yesterday I swapped from the tater plow to the tiller to prep some rows for fall garden.
Yup... Lost the lower arm pin. Tiller stopped and turned left but luckily it didn't pull the pto apart. Glad I hadn't read post #30 yesterday. Whew. Never even thought about this stuff.
In reality it was my fault, the hitch pin was really hard to get on. I thought I had pushed in on but may not have. No need to worry about that now, I replaced it. Not sure where the other is though.
May need to get the metal detector out after the season is over.