Why would they have a pin,was it a night stop?
There is no chance for a forgotten steering pin,as they would not have been able to taxi to the rwy....unless,of course the tug left them straight on CL.
And I think I never saw a tech log entry regarding pin insertion during night stop.
They didn't saw it? ...well ,maybe it is not common to insert locking pins during stops.We never do it on the 737 . So, yes ,we are not normally checking for the pins,except before departing base.