Palace have still not secured a play-off spot after Stephen Dobbie's first-half opener was cancelled out by Jordan Rhodes before the break.
And Holloway was left fuming after Rovers defender Grant Hanley appeared to bundle over Glenn Murray in the box in the second half.
Holloway said: "He (Murray) could have scored today. Without being shoved 10 yards. Am I exaggerating or not?
"Without being shoved completely as you're going to head it, onto your back, he would have took the penalty.
"Without them cheating at that point, because that's what it is isn't it? You can't defend properly so you shove somebody over and the ref didn't see it, what more do you want him to do?"
Palace need one win from their two remaining games to guarantee a top-six berth and Holloway felt they let a golden chance slip through their fingers.
"It was a very solid performance apart from Rhodes' goal, but the rest of the game I thought we were excellent," he said.
"Damien Delaney had a header and on any other given day he puts that in. We've hit the bar twice and do I need to mention the most blatant shove on anybody I've ever seen.
"The rest of the game was good and Blackburn played their part but I thought we were solid, looked in control of things. It's still in our hands but I thought it should have been over today. It was a very thorough away performance.
"Generally, I'm pretty bemused how we haven't got three points."