If you use kismet (Linux) you should see it, typically, IF someone else attaches to it and uses it.  While SSID's aren't broadcast when they're hidden, they still HAVE to transmit in the packets, with authenticated machines / machines that KNOW about the AP, to talk to it, and kismet will then pick them up.

You could force a deauthentication against an already authenticated client, and get the SSID that way (that's how I would get the SSID, by forcing a client to resend the SSID in an authentication packet.)  This is also how you go about speeding the process with WEP cracking, etc, as you need enough weak IV's to crack the key, and by deauth'ing attached clients, repeatedly, you force them to resend the SSID and data enough to crack it.

That way, because the client is not yet associated, fully, with the AP's encryption in play, the SSID will be transmitted in the clear, as it would anytime a new client would associate to the AP.

Edit:  To answer your last queston:

and what if no one appear to connected to it not in kismet at least !! ?

IF nobody's connected, yet, and you don't already have the SSID, you'll have to wait until someone tries to connect...

I'm not getting how you see it in Wireshark but not in anything else. All airodump does, is dumps all the packets that the wireless card sees. Sort of like TCPDump, but wireless.

My thoughts: Are you using the hardware that can talks the same freqs as the ap and clients? a/b/g/n? Something else?

Are you sure, since you're only seeing it in 1 packet capture device, that it's not a false positive?

are you sure it's actually the AP, and not someone's client trying to connect to an ap?

If the data is encrypted, you'll still see it transverse the air with the sniffers, you just won't be able to read it.

well i'll try to get more info next time to help u guys understand me more thanks for replying so far anyway