I think it is pretty clear that he was referring to TP. Remember that he also asks Cadsuane to use her well to open a gateway if something goes wrong. Presumably, if he could use some third creator given power, then that would work in Far Madding too just like the TP, and Rand could have opened a gateway himself.

I do admit however that when they pass into the effect of the Guardian, Naeff has a very visible reaction when he loses Saidin, but Rand shows no reaction at all. I suppose that could be a subtle clue that he still has access to a different power and as such the loss of OP was meaningless. I think it more likely however that Rand/LTT is simply old and experienced enough that such things no longer bother him the way they do the much younger and more inexperienced Naeff.