Vulcanian expedition
The Vulcanian expedition was an unspecified Starfleet mission conducted during the mid-23rd century. James T. Kirk served on the expedition, along with . 

Kirk hadn't seen Timothy between the expedition and the 's stop at Starbase 11 in 2267. ()

See also 
 Vulcan Expeditionary Group

Background information 
As "Vulcanian" was used as an alternative term for a Vulcan, it is probable this had something to do with the Vulcans, or .

The date of the expedition can be narrowed down to some time between Kirk's graduation in 2254 and 2267, since Kirk mentioned having last seen Timothy then, but having not seen any of the others since his Academy graduation.

According to the novel Strangers from the Sky, the Vulcanian Expedition was an event where Starfleet sent four starships to Vulcan as a show of unity. However, its real purpose was to intimidate the Vulcans into joining Starfleet after several Federation members, particularly Tellar, complained that the pacifist Vulcans did not contribute enough to the defense of the Federation. The commissioning of the USS Intrepid with an all-Vulcan crew was the result of the expedition. Kirk participated in the expedition as navigator of the Republic.

According to the novel The Captain's Oath, the Vulcanian Expedition was an eight-month joint survey of deep space by the Vulcan Expeditionary Group and Starfleet. Kirk participated in the expedition as first officer of the Eagle.

External link 
 

de:Vulkan-Expedition
Missions and expeditions