Hello Bunblebud, Welcome to the group.
Just wondering why you need to find the source of the spring?
If you can work out the general direction of the pipe, you should be able to follow it, using a thin metal rod prodding through the soil,
to find out where it's blocked, should it be feeding a water trough somewhere?
Someone may have water rights on it.
Just a thought, you may be better redoing your intro with a bit about yourself, and putting the water question under land management in the forum?