Don’t know the reason why you would go two years without math (and you don’t need to share why on this forum, as it’s none of our business). But if that’s the case, you may have a bigger problem than not having a junior-year math teacher to do an assessment.
Suggest you take up this issue with Admissions and/or B&G officer. It’s highly unusual and if it’s not out of your hands, I believe it would be looked upon unfavorably. USNA — all SAs — is a STEM-centric institution. They seek people who’ve shown themselves capable of higher math. So you’ll need a very good reason for not having math for two years.