Crow Hop?

[SC Ump]

From what you have described, I would say that is a crow hop. But, there might have been a misunderstanding in your communications with the umpire.

Remember that the "non-stride" foot does not have to remain motionless. The pitcher could slide it as her first movement, as long as it remains in contact with the pitching plate. A dance instructor might interpret this as "a step" where by softball rules it is not.

And of course, during the delivery that foot can also be drug away from the pitching plate, thus actually not being in contact with the pitching plate at the time the ball is released.

The pitching rule is quite technical. A comment in passing to an umpire on the field, or a post on a bulletin board that does not mention all the specifics, might lead to difficulty in understanding the whole situation.