Pre-tail times would have seen Timothy colliding with the well-dressed stranger and falling on his rear, but as it was his new cat reflexes had him able to stay on his feet, keep his ice cream and catch the other guy before he fell too. Alas, his tail had to get involved to help him keep his balance enough to be that graceful and it had whipped out to the side to help him stay on his feet. He automatically curled it back in under his robe as soon as he had his bearings, but there was still a chance it had been seen, which is why he never went to the Muggle world anymore.
"Oh, are you okay?" he asked immediately, not wanting to accidentally spill ice cream on the guy so taking a slight step backwards which allowed him to scrutinise the stranger for any damage at the same time. "I'm so sorry." he apologised, assuming it to be his fault.