So what happened to this feature..? Maybe I've just lost my mind and it's just hiding, or maybe it's gone.

I think Forum Search is a feature available to paid toolbar users... if you don't have those you won't have the search. If you do have toolbars then you should have it!

As far as I know you only get it when you get the timer package.

Timers Package 5.00 Credits

Boost your productivity with the following features:

• Attack/Petty/Felony/Jail/Flight/Alt timers: The game will notify you when you are eligible to do your next action.
• Jail Stats Display: Displays how many jails you have done recently and what XP tier you are currently in.
• Western Union Money From Any City: Transfer money to your central bank from any location.
• Informative Locals: Online players are displayed in bold for easier identification and tracking. Displays number of TylerDurdens that are currently in your location.
• City & Drug Specific Tips: Maximize your profit by checking on prices before you fly. Get tips by city or by a specific drug.
• Search Forums: Search the forums to find matching threads.
• Profile Notes: Save personal notes on each characters profile.

I believe you get 7 days of timer perk for free from the start of a new character. After that you must purchase them yourself.

Sounds good, thank you everyone :)