A petition may be filed at any time prior to the sale or other disposition of the property or carrier involved pursuant to administrative forfeiture, but a petition in regard to property or a carrier which has already been sold or otherwise disposed of pursuant to administrative forfeiture must be filed within three months from the date of sale, and must contain the proof defined in § 72.34(b). Acquisition for official use is equivalent to sale so far as remission or mitigation of any forfeiture is concerned.