Actually the way most VCs say no is either by not returning your phone calls, or by saying "looks interesting; let's keep in touch," while not actually giving you a termsheet.
Things change fast in the startup world, so VCs always want to leave the door open in case you suddenly take off. (Taking off can mean becoming popular with users, or just other VCs.) As a rule they reject you in ways that can be claimed later not to be a rejection.