Insiders say Lampard was “the angriest they've ever seen him" after Alonso, who was subbed at half-time, made for the bus instead of sitting among with other subs in The Hawthorns stands.
Alonso, 29, was apparently seen returning to the pitchside seats about 15 minutes into the second half.
But it is believed he had originally sat on the Chelsea team bus by himself after taking a shower following his half-time hook.
A source said: “The players were saying they have never seen the manager like this.
“It kicked off after the game and he was going mad at Alonso.
“Some were talking about how they'd be surprised if he plays for Chelsea ever again."