Using the REFiD is correct. BASEIds only appear in the game world as items inside containers. As soon as you drop it on the ground, a REFiD is created for it. Everything you see in-game is a REFiD. You want the correct Lydia, which is REFid a2c94. I've used this several times when she is stuck in the landscape or there appears to be a navmesh issue:
prid a2c94 moveto player
If you don't see her when you do this, perhaps she is disabled:
prid a2c94 disable enable moveto player
Other checks - she shouldn't be dead:
prid a2c94 getdead
should return 0
You can resurrect her as a last resort
prid a2c94 disable enable resurrect moveto player
If there is an error when you type
prid a2c94
Then something is wrong. I can't imagine that she would not be a persistent REF. At this point, not having a CK, I can only guess. Do you have any plugins from mods? Right now people are hex editing them - maybe one of them deleted her?