48 CFR §19.502-10

1. (a)If a small business set-aside acquisition or portion of an acquisition is not awarded, the unilateral or joint determination to set the acquisition aside is automatically dissolved for the unawarded portion of the set-aside. The required supplies and/or services for which no award was made may be acquired by sealed bidding or negotiation, as appropriate.
2. (b)Before issuing a solicitation for the items called for in a small business set-aside that was dissolved, the contracting officer shall ensure that the delivery schedule is realistic in the light of all relevant factors, including the capabilities of small business concerns.