This could have happened for several reasons:

If the order is in the Account Manager status or later and if the Order History on the review page shows the order being created but no Approval then an external account was used. An external account is an account not in the workgroup. It would have been picked by using the magnifying glass to search and use an account for the order. This behavior may be changed by having the Departmental Admin change the workgroup setting "Require Approval For External Accounts", or by adding the external account used to the workgroup.

If the Order History has a line for the Approver that states "automatically approved" then either the requester and the approver were the same person, or there was an Auto Approval created for the account or user.