Good to hear that the repair woked and is holding together. Dont be too disappointed though if it resurfaces after additional use.
Was/is this a custom TI frame?
Two common causes for a TI frame to crack in the weld: 1) Poor prefit/too much space and 2) temperature control. In the case of poor prefit, the welder had to fill the joint space with the puddle. The joint flexes, the weld breaks at the weakest point - the weld. If this was the original cause, these are a real challenge to repair correctly and permanently. Hence, the tendenancy for them to resurface after additional use.
The other is temperature control. During the welding process the joint cools too quickly resulting in a weak joint. Inexperienced welder - wasn't pushing the puddle. The joint flexes and eventually cracks. Much easier to repair, and if the repair is reasonably well done, it does not regenerate with the stress of additional use.
Be really vigilant hereonin. Check the joint religiously, each time, every time, all the time - no exceptions. TI is very strong but brittle - it is not forgiving. A structural failure at speed on any frame aint fun...