User blog comment:B214/Chapter 499: Gray & Juvia/@comment-24784846-20160829150711/@comment-7418318-20160829162719

I'm not sure if you can really say that he "can't" see her anymore. It's more that he chose not to (for good reason sure, since it was what Ultear wanted, but it was still his choice to go along with it).

He saw her in her current form, so he should be able track her down and see her if he were to put the effort and time into it.