What does it mean on Facebook when there is a mobile symbol but no 'Last Active' number?

[Jack]

Usually when a certain somebody I want to talk to is online, you see the usual green circle. Although when she's offline, you usually see the mobile symbol saying 'last active 11 minutes ago'

So if you get the 'on mobile' does that then mean she's appearing offline to me?

[Amelia]

It means that she is on her phone but not on Facebook xxx hope this helped

[St.3240]

It means they are connected to the internet with their phone, but they aren't actually on Facebook because if they were, the green circle would be there. The phone symbol is just a way of showing that they are connected online with a phone. I know its mis-leading, I think that's the explanation.