I just joined to debunk some of the assumptions about Navy shipborne operations. As a former Electronic Warfare Technician, I was in charge of EMCON conditions on my ship (a tin can). Radiation is commonly turned off so we can steam undetected. Then you are back to just 3 sensors in the dark. ESM (detecting other radars - good for azimuth but not range detection), Sonar (similar, under water azimuth location), and lookouts. The officers hated Emcon, and would try to "sneak a peak" and turn on a radar for a couple minutes to check out what a lookout saw. And my EW system would instantly detect them, and call the bridge to shut it down. We would often cross entire oceans, totally with everything turned off so the enemy couldn't see us. There was no super secret method to avoid ships....we just used lookouts. Barely trained cooks and such, but remarkably few collisions at sea. Though I was involved with one in a battle group once. Yes, we were in Emcon.
A Snoopy team is a glorified lookout. How do I know? I was one of those too. I had the ships cameras, ran the darkroom, and took many photos of Soviet ships, planes, and surfaced subs back in the 80s when I was in. Was I highly trained to photograph? Um...no. The guy leaving the ship gave me the camera kit, showed me the darkroom, and left. 15 min talk, I was on the team! But as an EW I knew a lot about Intel, that's kind of what we do.
Strange lights at sea happen. It's no big deal. Today if the TAO or bridge officers were concerned about it, they would have lit off the surface and air search radars. Maybe they did.
And the "high altitude" discussion is kind of silly too. A few thousand feet is low altitude, VFR rules stuff. 15,000 or higher? You won't see a drone. Maybe it's lights....maybe. So it's a paradox, either the drone wasn't that high, or it was something else. But we'd commonly have helos and LARGE target drones fly over us at 5,000 feet or so. And you can see them well in the day. At night...nothing but lights.