In truth, Lex did not need anything to detect time fractures. His affinity for time, which still had not been sealed yet, reacted perfectly to time fractures in a way that let him know where they were.
Lex also had absolutely perfect control over his entire body, down to every single hair, so he was absolutely certain he wouldn't accidentally touch the cracks. But considering the seriousness of the matter, he still took a few moments to compose himself. Or a few hours.
Honestly, by now, he had no idea what rate time was flowing at. His personal quest from the system still showed over 300 hours left, but according to Giselle the time they had left was much less.
He had no idea how her watch was able to calculate the remaining time for whomever time was flowing the fastest in this entire bubble, and now wasn't the right time to ask either.
Lex closed his eyes and retracted his spirit sense. He even withdrew his sense of touch.