sometimes it just means that they are getting comfy.
try having a blanket under the rabbit when in your lap. don't fold itor anything just kinda set it all down and put the bun on top of it(make sure it is one you won't be sad if a few holes get in it), andyou will find that a lot of rabbits like to move blankets around tofind that perfect spot
here is one of my rabbits, winnie, tugging the blanket into perfection. . .
YUP! lol! I think it is verythoughtful of him to let me know! If I don't put him downwhen the digging starts, I will then get his butt backed up into myface! Then I know I better move, fast! lol!!