After their victory, a member of Slavia’s staff called Soucek on FaceTime as players and coaches celebrated on the pitch, according to Mail Online.
Soucek spent 15 years at Slavia before joining West Ham in last summer’s transfer window.
Leicester are of course among the Hammers’ rivals for a Champions League place next season, with the Foxes in third place, four points ahead of Moyes’ men.
Arsenal visit the King Power Stadium on Sunday looking for a first win in five Premier League games as Arteta’s side bid to climb back into the top half of the table.
They go into the game boosted by Thursday’s 3-2 victory over Benfica, which saw them reach the last 16 of the Europa League with a 4-3 aggregate win.