I'll Show You Mine If You Show Me Yours
Rebel Storvik had located the vessel in which the crossovers had made transit from their own universe to this one. As far as he knew, not only did no one else know where the USS Obama was, but they were not even looking for it. The assumption would be that the crossovers had come through via transportation, as they had always done in the past. Rebel Storvik had what was known to the Ferengi as a “hot commodity.”
However, he had no actual direct use for it. He did not intend to risk his own life on any traps which had been left behind, but he had no intention of turning it over to anyone else without getting something in return. The thing that he sought was contact with the actual personnel who had crossed over from the other universe, with the goal of returning with them and leaving this universe behind. In order to do that, he needed to know the current status of the crossovers - almost certainly captured and being interrogated.
To get the information he sought, he would have to contact Grace. However, he did not know where she was or who she was with; nor did he want to give away any information about his own situation just yet. He decided to open communications with her by sending a single character of text to her PADD:
“ ? ”