The only time i have seen that was on a seedling with one less node. It was caused by difficulty shedding seed hull. Nothing real bad just the normal hull getting stuck.
Sorry for the delayed response. My ISP went down for 2+ days.
I suppose a grasshopper could have chewed it off but it's the only one out of 9 with any physical damage. Also, there's no scar.
I did notice 3 or 4 seedlings had a bit of trouble shedding their hulls this time but those were on the ends of the cotyledons and I see no significant damage from that.