[Q] Reversing Bootloader to locked topic

Hi guys,
I just updated my HTC M8(european) to Lollipop and after updating i hardreset the phone, which caused that all my photos and videos are wiped out. As I understood, undeleting files requires access to root and rooting is not possible without unlocking the bootloader. As I found out, it is only possible to unlock the bootloader by the HTC provided token and my question is:
1) is it possible to re-lock the bootloader as the original?
2) if re-locking requires S-OFF, is there any other option then the 25 USD sunshine?

Thanks in advance!