What does a wifi antenna look like in a Hotspot?
The pictures aren't very clear, but it appears the antennas (yes, multiple antennas) are not on the board itself.  They would seem to be in the back cover and/or the clear plastic caps with flexible circuit boards inside (the orange colored stuff inside the clear plastic parts.)

I say this because I see 5 parts that appear to be RF connectors.  Those are the small silver squares with a round black thing - the black things have holes, so they would seem to be connectors rather than buttons.

Each of the apparent RF connectors has a set of spring contacts next to it.  I expect those are the connections to the antennas in the housing.  If you look at the clear plastic parts, they have matching connections.  The flexible circuits inside are then the antennas.

There's probably matching spots on the back housing for some of the connections, with antennas embedded in the housing.