In direct relation to Was Kevin Mitchell Safe?, I now present Was Wally Backman Safe?
1987 Topps #48 Wally Backman
As best I can tell, he was safe. Going over all the Mets/Pirates games from 1986 this picture looks to have been taken during the June 15th game at Shea Stadium. It was the bottom of the 4th inning and Wally hit a lead off single to right field off Pirates pitcher Bob Walk.
1987 Topps #628 Bob Walk
Next up was Keith Hernandez...
1987 Topps #350 Keith Hernandez
...who doubled and Backman came all the way around from 1st base to score. Hernandez advanced to third on the throw to home. The Mets went on to win the game 4-1 and eventually the World Series.