Bill Simpich: Who found Oswald's wallet?

Over at JFKFacts.org, Bill Simpich has started a great discussion about the second(or third) wallet.

It's interesting that an FBI agent now accuses the Dallas PD of covering up evidence that would've tied Oswald to the Tippit murder. Why would the police have covered up evidence that incriminated Oswald? 

http://jfkfacts.org/assassination/on-this-date/oswalds-wallet-planted-at-the-tippit-crime-scene/

Several people at jfkfacts.org have commented that the only plausible reason for covering up this wallet at the Tippit murder scene was if the police did indeed remove a wallet directly from Lee's person upon arrest. Otherwise, why not use the incriminating evidence to tie him directly to Tippit's murder?  I tend to agree. Once the veracity of the story of this wallet's "discovery" is accepted, one must conclude it was a plant.