It's interesting, however, to see that the small brain size of mice is still enough to support it. I suspect it has something to do with the hypothalamus/whole brain size ratio.
Since rodents have been established to be capable of experiencing entrained trauma responses (stress hormones, hypervigilance, disturbed sleep habits, reduced sociality and panic behavior to audio triggers) and the OP establishes non-parental caregiving behavior, the combination of the two suggest it's likely that they can feel some version of guilt, shame or grief in the instances where their resuscitation reflex is unsuccessful.
Papers:
A neural basis for prosocial behavior toward unresponsive individuals https://www.science.org/doi/10.1126/science.adq2679
Reviving-like prosocial behavior in response to unconscious or dead conspecifics in rodents https://www.science.org/doi/10.1126/science.adq2677
An innate drive to save a life https://www.science.org/doi/10.1126/science.adv3731
An innate drive to save a life https://www.science.org/doi/10.1126/science.adv3731?url_ver=...
In this Times piece, a study author, interviewed by NPR, was part of the paper: Reviving-like prosocial behavior in response to unconscious or dead conspecifics in rodents https://www.science.org/doi/10.1126/science.adq2677
It's strange all three papers have different authors from different edus (colorado.edu, ecla.edu, NIH, esc.edu)
