I'm of the opinion that 'fetal resorption' does not happen... there's no absorptive epithelial tissue in the bovine uterus. But, people - including veterinarians and reproductive specialists - continue to make the claim to their clients... but I'm not buying it.
Rather, my stance is that there is degenerative liquefaction of embryonic/fetal/placental tissues - resulting in noticeable vaginal discharge... or, expulsion of conceptus/fetus and fetal membranes, without anyone ever seeing them...the cow just comes up 'open' or returns to heat after you'd thought or confirmed her as pregnant.
Had a 10-yr old cow that went to the salebarn this morning. We'd pulled her in to the 10-acre lot behind the house about a month ago, as she was getting close to her delivery date, based on when we'd seen the bull service her - and she's got horrible teats, so we were afraid we might have to help the calf get started. After a couple of weeks... all of a sudden, she didn't really look pregnant anymore, and her udder was regressing... I palpated her... open, with a big, involuting uterus... she'd evidently aborted (as two others had done recently, most likely due to Neospora)... but we never saw the fetus or membranes. There ain't no fetus in there any more! But just because I didn't see her dump it, doesn't mean she 'reabsorbed' it.