Every time Toshio gets the drop on Cat's Eye. Some examples:
The very first manga chapter had Hitomi trying to steal a gem, only for Toshio to pop out from under the gem's stand and grab her before she can realize what the hell is happening (Hitomi only escaped because Toshio was too stunned to keep her there once he accidentally groped her).
Hitomi was committing an unannounced heist, and as soon as she grabbed the painting she found a letter from Toshio asking for a meeting with Cat's Eye. At the meeting, Toshio explained her he noticed part of Cat's Eye pattern: they steal Cranaff paintings with a particular variant of the signature (he didn't know that particular signature identified them as their father's works with the signature replaced, but nobody other than Cat's Eye, Nagaishi and the Cranaff Syndicate had the knowledge to find out).
Doubles as Nice Job Fixing It, Villain: in one occasion an art smuggler who had captured Toshio and was being chased by the Japanese police, his own country's police and Cat's Eye wondered if the latter had noticed he had a Cranaff painting, with Toshio's face showing he finally understood something that was bugging him before then.
Later he found a Heintz painting targeted by Cat's Eye before Cat's Eye did, and without even realizing Cat's Eye targeted Michael Heintz paintings only. How? Easy: between Cat's Eye targeting Cranaff's paintings, him being Heintz's main apprentice and Cat's Eye having already targeted Heintz's paintings, he realized that Cat's Eye would have probably targeted what was Heintz's most famous painting.
In one occasion Cat's Eye targeted a painting in a museum surrounded by a cliff on three sides with the sea in the end. Hitomi as Cat's Eye grabbed the painting, ran to the cliff to jump (with a backpack glider to slow the fall enough to survive)... And found that Toshio was there, who had realized she would try and escape from there and checked the area for whatever device she planned to use.
At one point in the manga Hitomi started dying herself blonde and wearing green lenses during the heists due the police having noticed her resemblance with the subject of a painting targeted by Cat's Eye (the subject being Hitomi's blonde grandmother). It worked for a while... Then Toshio realized Hitomi and the blonde Cat's Eye were identical.
Thanks to both the resemblance between the blonde Cat's Eye and the painting mentioned above and a comment about Heintz having painted a group of a mother with her two daughters that could help identify Cat's Eye (Ai wasn't born yet at the time), Toshio realized that Cat's Eye were Heintz's two daughters, and, after Cat's Eye roped him in destroying the painting, found the place where its draft was kept before the sisters.
For a heist in a restaurant set in a rotating platform above an hotel, the girls placed sleeping gas emitters in the bottles of a particular liquor and Hitomi had it given to the undercover cops set there. By Toshio's orders, all the cops had gas masks, forcing the girls to act on their much crazier plan B (accelerating the rotation to the point the cops would be pressed on the windows).
Most of Cat's Eye's heists where Hitomi grabs solo. Why? Easy: she always escapes the most dangerous possible way. Among her escapes we have her jumping down of a cliff into water (and, averting Soft Water, it had been explained that a jump from that height would have killed a jumper. Sure, she had a backpack glider, but it was still dangerous as hell) and jumping out of the window of a skyscraper using a rope with a weight acting as pendulum to reach her escape way (a small error with the timing and she would be dead).