isn't there the possibility of moving the landing gear lever during the ensuing circuit
I suppose any mistake is possible!
It is worth noting that a 172RG, like nearly all RG wheel landplanes has an effective landing gear position warning horn. That should be consider a luxury, and a careful pilot should directly assure intended landing gear position without the aid of warning systems. This should be done in all cases of RG airplanes by the pilot thinking about what they are going to do, then thinking about what they are doing, then confirming what they have done, then speaking the checklist to assure the intended configuration. The thinking, confirming, and speaking actions should make a mistake extremely unlikely, leaving only a systems failure to be the unknown factor.
Amphibians and wheel ski planes are examples of types for which the pilot must select the landing gear position correctly, and confirm it, generally without the aid of a warning system. Similarly, one might decide to deliberately land an RG landplane with the wheels retracted (ditching/off airport forced landing). in which case, again, think, confirm, speak what you have done. When I train in these types, regardless of whatever warning systems may be built into the airplane, I insist that the pilot observe the intended landing gear position, and surface and then state them out loud, preferably downwind. It'll be one of: "Wheels are down for runway landing"/"wheels are up for water landing"/"skis are extended fro snow landing"/"skis are retracted for hard surface landing"/"wheels are retracted for ditching", etc. With such discipline, wrong landing gear positons are much less likely.
And, it is worth noting that many RG landplanes use a throttle(s) position sensor to operate the gear position warning horn. So, if you carry power through the landing, and forget the gear extension, you may have defeated the warning system. In terms of warning systems, silence is not a warning. So, when a pilot hears silence, there should still be an expectation of confirming as a manual action, and speaking the outcome in terms of the expectation.
Two years ago, I did test flying (for another reason) on a Cessna 185 amphibian, in which, at some point in history (I'm thinking at least five years earlier - so four annual inspections ago at the time) the manual landing gear extension system was rigged backward, so a down selection, with operation of the handpump would raise the landing gear. It indicated position correctly, but what would the pilot think if they had thought that they had just pumped the gear down?
Operate the landing gear as you intend, with thinking, confirmation of what you have done, and speaking the observation of the resulting selection!