Based on how Excel works, VLookup doesn't need to be sorted, if the 4th parameter is FALSE. The 4th Parameter determines whether an approximate search is used or an exact match is used. by default true is used and an approximate search requires a sorted range. However, if set to FALSE, then the range doesn't need to be sorted. the value is checked against the entire column of cells and can be unsorted.
We process spreadsheets that use VLOOKUP with 4th parameter set to FALSE and unsorted data in range. These work in Excel, but not in Telerik Spreadsheet processing.