If police obtained a search warrant to seize a suspect's electronics on suspicion of illegal material on their hard drive on account of them having access logs that the suspect viewed such material, (by, for instance seizing the servers of the web host and looking through its database to find the access logs of its visitors) if they are unable to find anything are they still able to land an indictment just from the access logs?
Added bit: What if as well the user had a user account on the website linked to an email address that identifies him/her, but no evidence of possessing any illegal content upon seizure (nor any evidence on his/her computer that he/she had registered, just the appearance of a personally identifying email address on the seized database)? And to muddy things further, suppose the website wasn't dedicated to showing illegal content but just hosted some (maybe with a legally negligent set of site rules), so it would be hard to conclusively state that the user was seeking out that illegal material.
Update to question
I recently stumbled upon this news article, which seems to purport that police aren't able to make arrests from an online footprint alone. Here are some relevant excerpts:
During the tour in February, Carly Yoost demonstrated the system, starting with a dashboard that showed a list of the "worst IPs" in the United States, ranked by the number of illegal files they had downloaded in the last year from nine peer-to-peer networks.
The software is able to track IP addresses — which are shared by people connected to the same Wi-Fi network — as well as individual devices. The system can follow devices even if the owners move or use virtual private networks, or VPNs, to mask the IP addresses, according to the Child Rescue Coalition.
Clicking on an IP address flagged by the system lets police view a list of the address' most recent downloads. The demonstration revealed files containing references to a child's age and graphic descriptions of sexual acts.
On top of scanning peer-to-peer networks, the Child Protection System also monitors chatrooms that people use to exchange illegal material and tips to avoid getting caught.
The information exposed by the software isn't enough to make an arrest. It's used to help establish probable cause for a search warrant. Before getting a warrant, police typically subpoena the internet service provider to find out who holds the account and whether anyone at the address has a criminal history, has children or has access to children through work.
Does anyone have any sources corroborating this statement? The consensus on the answers on this question is that arresting someone in this case is possible, but difficult. Here, it seems to suggest that what seems like fairly substantial evidence is not enough without a search.