Looking at recipes it looks like 6 row is not used much other than Wheat beers
As a rule of thumb this is true, however...I have done recently a pseudo Hamm's beer clone, 2 slightly different American Dopplebocks, and am planning a Stout all with 6-row as the base malt. It i
s a base grain after all. The reason most people do not use it is because it takes about 1 pound extra to get the same starting gravity as using 10 pounds of 2-row.
My LHBS has had crazy good prices on 6-row and so I have been using it in MANY of my brews. I have already brewed and am drinking an American smoked brown and had a 1/2 bbl of yellow fizzy beer that was 90% 6-row and many more that used it as 1/2 or less of the grain bill.
It is not a bad malt and your grain bill/beer may be VERY salvageable and still do-able if we have the requested info.
We need to see the original recipe and know what the quantities were and of what was subbed for the 6-row...
FWIW Munich II is a fairly uncommon malt (folks before made it sound like every LHBS should have 50# in stock.) However normal Munich may have been in stock, if so it would not be all that hard to toast a pound or 2 in your oven (there are ways to calculate it) and make your own Munich II malt. If your LHBS does not have standard Munich a decent sub is Veinna, as mentioned.
Just because you have a little extra base malt doesn't mean we still can not get this headed in the right direction...