The only signs my lacto infected beer showed coming out of primary was a slight sourness and something not-quite-right. I was suspicious enough though to not rack it to a keg and just cover it back up and wait another two weeks. 'Two weeks later, it had the characteristic slime in it, and tasted even more sour. It still looked ok except for the small amount of slime, and smelled a bit off. It tasted like **** by that point, though.
No doubt in my mind at all that it was lacto at that point!