Mines are also NOT uncounterable perpetum machine that'll always blow up under critical opponents units.
In fact, high tier players rarely fell on them, because they lead their attacks with sweepers.
Exact same case here.
Player was prepared for mines and you didn't relied on anything else, therefore you've lost.
Mines protect your flanks or at least slow down the advancing enemy forcing them to clear them or keep a sweeper nearby to keep them revealed, detecting mines while moving unravels both of those unique coh2 complexities and is bad both for balance and unit variety while dumbing down the game by giving you a unit that has too much combat value relative to its utility much like the soviet and ost halftracks losing the ability to reinforce when upgraded.