Yes!! Other people experienced this crazy unique event happen too!! My co op partner and I had this happen to us twice and we theorized every little thing we could as to why it happened. We thought that maybe Bungie was blowing us a kiss after we survived a run through of the '??' tunnel connecting the Grottos and the Refinery... on foot. Both times the events happened, it would initiate when we were in the area - not minutes after surviving that horror of a cave.