John Rudd crossed for a converted try on the resumption to give the Exiles the lead, but Worcester hit back with a penalty try, converted by Walker.
Lamb's penalty on the hour levelled it but Warriors continued to impress and push for a winning score as they had to settle for a second draw against one of the Premiership's top two in consecutive weeks.
"Toby (Booth) and I were joking before the game about another 12-12 draw, but we seem to have the ability to draw these games," said Ruddock.
"I thought it was a winning performance by us though - we deserved to win the game and were the stronger side overall.
"We made less errors and, in fact, the London Irish skipper Bob Casey, who I coached many years ago at Leinster, came up to me after the game and said he thought we'd deserved to win.
"In some ways I'm pleased that we've come to one of the top teams in England and stopped them from getting a home victory. But in another way I'm disappointed we didn't go the extra mile and get the result.
"We're not a million miles away, but it is just a case of making that knock-out punch to deliver the result.
"We could have tried for the drop-goal at the end, but we don't want to take the initiative away from our players either," he added.
"If that kick from Jonny Arr had bounced into Miles Benjamin's hands at the end we would have all been rejoicing what a fantastic bit of play it was.
"There was space in behind and it would have been a tough drop-goal for Willie Walker in difficult conditions with a greasy ball. Jonny's kick is not something I'm going to lose sleep over.
"Overall, I thought we battled hard, our scrum was strong and our line-out and maul were good. Our breakdown work overall was very good, but we did seem to give away a lot of penalties there. The breakdown is a big discussion area at the moment with regards to getting that consistency with the interpretations.
"Irish tried to play at times off quick line-outs and counter-attack as we knew they would, so it was important for us to defend well. There was just one defensive lapse by us in the second-half when they broke through.
"However, we haven't been beaten in our last three league games now and that will give us the confidence to press on. Obviously we want to win every game, but it is such a tough league, and the main thing is we are not getting beaten.
"Our performance levels are good enough to win - certainly in the last two games against the top two teams in the league - and we have to take a lot from that."