Not in 61.57, but there could be a AC or something, right?
Not really. You won't generally find an AC that directly contradicts an FAR.
FWIW, may this blurb from FAA Order 8900.1 - Flight Standards Information Management Systems will put you on track. It's a sample manual for balloon competitions at aviation events submitted in connection with the FAA Waiver process:
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Each pilot must hold the appropriate pilot certificate (Private or Commercial) with Lighter-than-Air Category and Free Balloon Class Rating. Each pilot must show evidence of current Flight Review (14 CFR part 61, § 61.56) and
must also show evidence of currency per § 61.57. Minimum hours as PIC per the organizers specified time must also be shown.
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But I am curious. Why would you think the FAA would find it any less important for a pilot to show landing currency for a dealing with the drifting of balloon with the wind in both normal and high wind landings situations and stabilizing it for passenger entry and egress than for dealing with the landing issues inherent in another type of aircraft?