Thanks for the reply. I will certainly try the twig, although my camera inside suggests that the bedding has not been disturbed since Thursday, which suggests that either the hog has left the box or it has gone back to hibernating. If the hog was using it as a day nest then it may be that the return to more normal temperatures this week may induce it to return.
I assume that a female hog will scout for a breeding nest first and that finding a suitable location may help her come into heat ? I would also imagine that female hogs would more likely abandon a potential breeding nest if disturbed than a hibernating hog ?
I will probably keep an eye on it for the next week. If there appears to be no activity I’ll open it up next weekend.