Being lost in the post will not "normanly" work, but worth a try !
I must spend 3 hours a week dealing with V5.s doc etc, Under dual noticification (sp) it is down to the reg keeper to inform DVLA when you have no futher intrest in the vehicle, by sending the r/h top yellow part to them, and getting the recipt back in the 3 weeks !
I sent off 3 docs after scraping to them back in sept,got the recipt, and still got 3 80 quid + fines beginning of the month
I send the hybrid doc away for colour change, did not see in in 2 months, lost in post !! still had to fork out for a dulicate