DC, if Vietnamese ATS gets no reply, it will eventually start a SAR phase, as it probably did. If being voodoo, it would be far better to wait until after contact with Vietnamese ATS, that way you would only be missed after the next reporting point, not immediately.
It's nominally a radar environment, so there may not
be a next mandatory reporting point...
Each minute you fly along the cleared route puts you another minute from your destination, wherever that is, and behind schedule.
A missed/delayed handoff at zero-dark-thirty isn't something the next sector is going to get immediately stressed about, unlike an identified target in your sector suddenly going dark.
In the event, Vietnam ATC (which seems a bit more competent than Malaysia's) did wig out, and after not much time elapsed (a previous poster to this thread said he was on-freq at the time...).