**Yes**, it has happened that some US votes have not been tabulated, and where this is known, not even *re*tabulated.

For example, consider the 11/22/2000 ["Brooks Brothers Riot"][1], that many believe had, (one way or another), a decisive effect on the 2000 US Presidential Election, wherein a small organized horde of posturing, domineering, middle-age Republican paid zealots were deployed to bully and delay Miami-Dade canvassers attempting to recount the 10,750 remaining [poorly-designed ballots][2] that their elections computer was unable to tally.  

[![enter image description here][3]][3]


The riot, planned by the notorious [Roger Stone][4], and ably orchestrated out of a nearby winebago made into an impromptu wireless command center, made it impossible for the frightened canvassers to complete the recount prior to the [deadline of 11/26/2000 set by the Florida Supreme Court][5].  So the 10,750 ballots were not counted as votes.

Three weeks later, voting on partisan lines, [the United States Supreme Court mooted the Florida Supreme Court's recount order](https://en.wikipedia.org/wiki/Bush_v._Gore), but nobody really knows, if those 10,750 Miami-Dade ballots had been tallied and if, (since [Miami-Dade usually votes Democrat][6]), the resulting votes had put Gore to win Florida, as to whether or not the resulting changes in public opinion might have inclined the Supreme Court to demur.


  [1]: https://en.wikipedia.org/wiki/Brooks_Brothers_riot
  [2]: https://www.presentationzen.com/presentationzen/2008/11/think-graphic-design-doesnt-matter.html?__cf_chl_jschl_tk__=5a33a451dfa463cd40a6ea9e0b6496e1b826a1b2-1599785911-0-AdMbDpuPGkTD9P3SFRARn0kWH4Rp5k4K88leH9gwMGp-B73bZ6k8gzuM96MngzqMpNKC9ubquh0VU-Bv3N76NyZMAR4WJ---r7ErouvG6DoAUcznrN6-2cUjxt7aPbYGfzIeZXm0eqFB-anyfSW2FN3ft9ERE53TSnzdg6DWOORkDXva6Phh3JFBo1mty46HSo29iGrNobpUTk0tb4D2VAPTTgq4SGi5zWAxP3QBFHteSnUGgzKgQqr2EaekhSr-xTGEObM4qe0P-fqwGCWdMc5hSU8eRSmpKfEST-rqXLOdzoZnP_TJi3clLGjkui94DJxpLyc3AuVPl-7rMfWCCfXg-aJCCUyEr5pFbVawaCxM
  [3]: https://i.sstatic.net/TAsyf.jpg
  [4]: https://en.wikipedia.org/wiki/Roger_Stone
  [5]: https://en.wikipedia.org/wiki/Palm_Beach_County_Canvassing_Board_v._Harris_(Harris_I)
  [6]: https://en.wikipedia.org/wiki/Miami-Dade_County,_Florida#Politics