Probable cause is not enough evidence to convict someone, but enough to conduct a further search to see if there is enough evidence for a conviction. See here (although this is US-focused, many other states have similar ideas): https://www.findlaw.com/criminal/criminal-rights/probable-ca...

Basically, they had the allegations and enough substantiating evidence to go to the point of looking for more evidence, but not to get all the way to an arrest/conviction. A search warrant is the next step.

EDIT: Also, the police have most likely downloaded the information, but you never know.