Is it this Saturday?
I see 1 UA and a few AC flights available for sale in GDS'es:
27MAY SAT YYZ/EDT SFO/PDT-3
1UA 565 J6 C6 D6 YYZSFO 0630 0918 738 B/F 0 DCA /E
Z6 P6 Y9 B9 M9 E9 U9 H9 Q9 V9 W9 S9 T9 L9 K9 G9 N9
2UA/AC 8698 J9 C0 D0 YYZSFO 0800 1025 333 B/F 0 DCA /E
Z0 P0 Y9 B9 M9 U9 H9 Q9 V9 W9 S9 T9 L9 K9 G9
3UA/AC 8272 J3 C0 D0 YYZSFO 1630 1908 223 M/F 0 DCA /E
Z0 P0 Y9 B9 M9 U9 H9 Q9 V9 W9 S9 T9 L9 K9 G9
4UA/AC 8433 J2 C0 D0 YYZSFO 1855 2133 321 M/F 0 DCA /E
Z0 P0 Y9 B9 M9 U9 H9 Q9 V9 W9 S9 T9 L9 K9 G9
5UA/AC 8251 J8 C0 D0 YYZSFO 1955 2233 7M8 M/F 0 DCA /E
Z0 P0 Y9 B9 M9 U9 H9 Q9 V9 W9 S9 T9 L9 K9 G9
As TK issued the ticket, I believe it is TK that would have to reissue it. I would call TK to confirm the ticket is exchanged - you should get a new ticket number. I am not sure if the Saudia workaround still works (you was able to view any e-ticket number on saudia.com), but it is worth to confirm if the PNR and the e-ticket match.