I agree with David - but I know that sme have taken the position that once a "distribution" has been processed and the "check" is un-cashed (but remains in the payor's checking account), that it can be escheated after the prescribed period of time.
This of course would only apply to "cash out" distribution and not balances in excess of $5,000 which couldn't be distributed without consent (absent a plan termination).
I happen to disagree that such funds can be escheated as simply moving the balance into a checking account is does not remove the assets from the "plan" (despite what some recordkeepers claim) and merely puts the plan assets in another vehicle for delivery to the participant. Failure to deliver (meaning actually transferring the assets TO THE PARTICIPANTS CONTROL (e.g. cashing the check) means the assets should be redeposited into the plans trust and dealt with per the terms of the plan. Forfeiture is an option, but as far as I know, one actually with "authority" but one the regulators seem to "tacitly" accept (at least, I've heard of no action against plan sponsors or others for doing so)....