Platt emerged as a 63rd minute substitute at the Meres Stadium to end a long injury lay-off following ankle surgery.
While United keepers Sam Long and Rhys Davies were relatively untroubled, ex-Pilgrim Dan Haystead had to make a number of saves to repel the visitors.
Boston (3-4-1-2): Sam Long (Rhys Davies 46); Lebrun Mbeka, Luke Shiels, Jean Leroy Belehouan; Ellis Myles (Keenan Ferguson 63), Tom Solanke (Ben Pollock 46), Will Atkinson, Trialist A (Trialist B 63); Jordon Crawford; Jaanai Gordon, Jake Wright. Subs (not used): Alex Brown, Scott Pollock.
Referee: Gary Caley.
Attendance: 268.
PIC: Oliver Atkin.