
Actually, these sound like classic nesting behaviors. Several pokémon native to the Mt. Silver range are capable of breeding with luxray, including absol (a rare find, but nonetheless), as well as ursaring and donphan. Even if you only lost sight of Sunlight for a day, that could be enough time for her to meet and, well, mate.
Keep an eye on Sunlight for the next few days. If she begins eating more than usual, you may be expecting an egg or two soon. The next step would be to follow her to find out where her nest is and to see if there is an egg to be concerned about, and if so, the step after that would be to convince Sunlight to let you help her (as opposed to electrocuting you on sight if you’re anywhere near her nest, which tends to also be classic luxray nesting behavior.)
Best of luck!