From what I understand, if his computer was seized as "evidence", he will not get it back. Ever. His best bet is to just buy a new one and start over, unfortunately.
As far as I know, here in Germany, if you/the evidence are cleared, you are supposed to get your confiscated stuff back - if not, you won't.
That doesn't mean, evidence doesn't get lost though.
This is not about his PC though, but his storage mediums the data is on. There are multiple, so not all 'should' go missing.
Without those storage devices, K7 has no backups for most of the characters daz configurations, so would need to create them from scratch, resulting in visual differences.
While there should be no evidence regarding the original accusations (crypto scam), the investigator(s) seem to try to make a case out of the visuals though, in portraying him as displaying forbidden content.
That 'should' also not stick, but might lengthen the process and might not be a case of just not finding the stuff they were looking for, but how the visuals are interpreted.