The minor would be the beneficial owner of the foreclosure proceeds. Taking possession of those assets held for his or her benefit by the county official conducting the foreclosure might as a practical matter be difficult. The official could probably insist on having someone appointed to act for the minor's benefit before disbursing the funds.
Often, someone to represent the minor's interest would have been appointed in the foreclosure proceedings. Selfishly, this is because there are problems associated with the finality of a foreclosure obtained against an unrepresented minor that might not be resolved until the minor is 21 years old. So, often a guardian ad litem would be appointed in the proceeding and make arrangements for disposition of the funds (often under a Uniform Transfers To Minors' custodial account with a parent or guardian as custodian).
Even if there is a guardian, custodian, trustee, or conservator appointed for the minor, the minor would still be the beneficial owner of the proceeds. In the case of a guardian or conservator it is splitting fine and technical hairs but there is a legitimate argument that the minor is also still the legal owner of the funds but can only act through his or her court appointed guardian or conservator because the minor lacks legal capacity.