Given that Hawking radiation includes separation of a virtual electron-positron pair, then why cannot it be the case that in the vicinity of a real electron it annihilates with the virtual positron?
The net effect must surely be that two real photons result and that for charge conservation etc the virtual electron must now become real (and displaced and moving slightly). The energy of the two photons of the annihilation event is also now manifest and will be spread around 40 Kelvin (the equivalent temperature of an electron rest mass). Conservation of energy is of course broken and should be evident.
Spectra of interstellar gas clouds do range across 40K and given their thin nature and that they sit in the vast heat sink of empty space then it is not clear to me why they sustain their temperature, i.e. they ought to rapidly cool. If this is the case then it may be evidence that the real electron and virtual positron annihilation is the source of energy that sustains their temperature and that energy is generated/released from that of the vacuum!