Borussia Dortmund ace Lewandowski smashed a four-goal haul against Real Madrid to help his side into the Champions League final last month but things could have been very different for both the Poland International and Championship side Rovers, had he joined the Ewood Park outfit three years ago.
Current West Ham boss Allardyce, who was in charge at Blackburn between 2008 and 2010, confirmed reports that Lewandowski was set to join Rovers, who were then in the Premier League, from Polish side Znicz Pruszkow in April 2008.
However, the ash cloud which brought much of Northern Europe to a standstill that month, prevented him from flying to England and the striker instead eventually opted to join Lech Poznan.
"Unfortunately he got delayed," said Allardyce.
"We didn't have a lot of money and he wanted to come. He was ready but after that he went to [Lech Posnan and then] Germany, which was a great shame for us and Blackburn.
"Obviously from his point of view his career has flourished from there, but that was one of those things you can't stop."
However, the former Bolton and Newcastle boss explained that wasn't the only occasion he has failed to land transfer targets due to unforeseen circumstances.
"I had Sylvain Distin nicked by an agent at the airport when I was at Bolton," he said.
"He took him off to Newcastle. We were all waiting on him, he landed and two hours later we were going 'where is he?' then the next thing we see he's signed for Newcastle on loan.
"And I remember Tomasz Kuszczak, the Polish keeper who ended up at Manchester United, was at the Bolton Wanderers hotel. Our secretary let him go without signing his contract and the next day he'd signed for West Brom.
"These things happen to you."