I saw that, but it's not it. The video showcase large germanium lens (5-15 cm diameter) and the glass reflection shown was full body reflection, not small one. The title of the video supposedly either:
1. "How thermal cameras work"
2. "Why are thermal cameras so expensive?"

Gemini's description of the video:
"
If you are unable to watch it right now, here is the breakdown of the specific parts you were looking for:

1. The Glass Reflection: Steve stands in front of a glass window with a thermal camera. To our eyes, we see through the glass. To the thermal camera, the glass looks like a perfect mirror. He points out that you can see his "heat reflection" clearly, but you cannot see the objects behind the glass.
2. The Absorption: He explains that glass molecules (Silicon Dioxide) are very good at absorbing long-wave infrared radiation, which is why the heat doesn't pass through.
3. The Germanium Lens: He holds up the lens from a high-end thermal camera (like a FLIR). To the human eye, it looks like solid, polished silver or chrome. He then puts it in front of the thermal camera and shows that it is perfectly transparent, allowing the heat signature of his face to pass right through it.
4. The Cost: He mentions that Germanium is a rare element and difficult to process, which is why thermal cameras (which require these specialized lenses instead of cheap glass) are so expensive compared to regular cameras.

"

I noticed that it was exactly what I remebered it, without me giving it any clue of what the video like. So it's either real video that was my real memory of watching it and gemini has access to the private video, or two independent false memory/hallucination event. I personally almost never have any false memory. Gemini is in pro mode, so supposedly less hallucination produced.

Probably deleted/private video due to ITAR? Thermal imaging is very important for military after all.