London Irish director of rugby Brian Smith hit out at the decision to award Cardiff Blues a controversial try in their 10-6 LV=Cup defeat.
The match referee consulted his touch judge before ruling Gavin Evans had applied downward pressure to the ball after a mistake from Tom Homer, and the 34th-minute score proved pivotal to the outcome.
"We've had a look at the tape and don't think it was a try," said Smith. "It was Hamer who pressed down on the ball and their player never touched it.
"It was a lottery out there. The pitch was a mess and it was a pity as we had so much to play for."
Irish must now rely on Worcester beating Saracens on Saturday if they are to reach the semi-finals, and Smith added: "Saracens still have to get a result at Worcester. We'll wait and see what happens."
Blues boss Phil Davies said: "We played some good rugby in the first half and showed a lot of guts in the second.
"For us to get a win against a quality side like that is very pleasing, especially as they brought their full-strength line-up."