Why did Nicky pretend to team up with Garriga?

Nicky's father had already done whatever was needed to steal the plans. Garriga's proposed con to sell fake plans to the competition had no significance in Nicky's father plan of stealing the original plans. Then couldn't Nicky and his father secretly sell the plans to the competition without Nicky having to team up with Garriga to pretend to be a disgruntled engineer and all that?

There doesn't seem to be any reason for Garriga to know that Nicky even exists for the plan to work unless Nicky's involvement with Garriga was instrumental in stealing the plans (which, if happened, I must've missed). The disgruntled engineer thing couldn't have been as a lure to be invited by the competitor because the plans were proof enough.