There are currently a couple of eBay sellers who insist that sewup tires can be repaired (although noone in his right mind would ever want to do it).
Description for Item #3615024551 (Tubular sew up Needle Kit) says "This was used to repair your tubulars. Nowadays we buy new tubulars but they can be repaired."
Description for Item #2180342500(Vittoria Sewup Tubular Tire Repair Kit) says in part "There's so much detail here, I mean, people used to repair their sewups !!! You can definitely use this kit, and your infinite patience, to repair a nice classic sewup. You can also just put these on a shelf to commemorate classic "attention to detail". "
Are these sellers nuts or is it true that, in the old days, people used to repair their tubular tires? If so, I'm certainly going to regret trashing all those punctured Italian hand-made silk sewups.