Some devices drop connections on 5Ghz. I'm not saying your phone does, but generally I find 2.4Ghz a lot more reliable than 5Ghz.
It's not dropping the connection, it just isn't showing in the list. If I connect to 2.4, it shows up. If I connect to 5, it doesn't. My wife has the same phone and hers is showing up on the 5 list and she's not even home.
Well, just because I should be able to see it. Otherwise, I should just forget about it but I want to find out why it isn't working as it should be.
Try a factory reset of the Homehub by pressing a pin into the recess button on the rear for about 20 seconds. If that doesn't work and your phone is connecting OK I would suggest that life is to short to worry about it.