If it isn't communicating to someone, perhaps it is communicating to other instances of the same symbol.

[Alucard doesn't like where his thoughts are going, but he has to let them do so. He recalls some of what Sypha told him of her time away and what happened in one of the villages. How it involved marks on walls for a greater ritual.]

It could be a part of a grander ritual outside of the kidnappings. Suppose there were a few of these located through the desert. They could help power something through a magic based connection.