Re-search the download using same terms you originally used. Then hopefully you will see both as separate downloads. There may be limited no. of people with that first one. Thus you may need to wait until they come online/you can locate them/they have free upload slots. Don't forget you can right-click a search result tab & choose to Get More Results.

BTW re: incompletes resuming from incomplete folder at correct % depends on the version of LW you have. It was introduced about a year or so ago to ensure it would do this. Earlier versions didn't & would instead resume at zero %.