You can still use a sold weapon.

[Bazsi]

I've sold one of my weapons and it was equipped and after i sold it it was still usable.

EDIT: It WAS equipped, but not on the weapon-select list.

Edited January 14, 2013 by Bazsi

[UkyoSonoda]

I had that happen also an then my game crashed when I tried to change it to a weapon I still owned.

[SwimmingRock]

Tried to replicate this bug, but it didn't happen for me. Sold My Bronco, which was equipped at the time, and my arsenal showed I had no pistol equipped at all. I started a mission and the game had just automatically equipped my AKLATO instead. I know you can't sell your last weapon of a type (tried that in the past), so I'm not sure what caused it for you.

[jnagoh]

I sold the starter rifle I had when I bought a new one and it sold out just fine. I did not have it anymore.

[UkyoSonoda]

It happened to me when I sold my Braton since I decided to keep using the Gorgon as my rifle. I switched to the braton to pull out some rifle mods I wanted to keep and forgot to change it back after I sold it. Saw it was still listed and shown on my character as equipped and when I tried to change it to the gorgon in the arsenal it locked up and I was forced to kill it manually. When I relogged in after restarting the program I had my Strun equipped in my long weapon slot.