Ten-man Albion were denied by a contentious 94th-minute penalty as they were held to a dramatic 2-2 draw against Charlton Athletic - extending their unbeaten home record to 14 matches in the Sky Bet Championship.
Josh Cullen slotted home from the spot deep into injury time to level matters for the Addicks after Semi Ajayi was adjudged to have pushed Naby Sarr in the penalty area.
Baggies substitute Hal Robson-Kanu looked to have curled home an 81st-minute winner when he sent the majority of the 25,356 present into raptures, Albion's biggest attendance of the season to date at The Hawthorns.
Fit-again Matt Phillips had earlier fired the Baggies in front from close range after just 10 minutes, registering his fifth goal of the season.
Yet Macauley Bonne headed an equaliser on the hour mark before teenager Nathan Ferguson saw red in the 67th minute for a challenge on Chris Solly.
Slaven Bilić's Baggies, bursting with spirit and determination, remain top of the table despite back-to-back home draws, and remain unbeaten on home soil since February.
Phillips, who missed the last two matches with a minor shin injury, marked his return with the game's opening goal, converting into the top corner from close range after captain Jake Livermore's delightful ball played in Matheus Pereira down the left.
Kyle Bartley came to Albion's rescue shortly afterwards to deny Macauley Bonne with a last-ditch sliding block.
Tom Lockyer diverted Conor Gallagher's 26th-minute shot over the crossbar while Chris Solly volleyed narrowly off target as the visitors looked threatening.
Phillips tested namesake Dillon Phillips at the other end before Sam Johnstone came to Albion's rescue with two great saves, denying Gallagher and Naby Sarr.
Darnell Furlong then headed just off target to draw an eventful first half to a close with Albion boasting a narrow advantage.
The hosts flew out of the blocks at the start of the second half, Phillips firing over when well placed before Grady Diangana was somehow denied by a superb save from Addicks keeper Phillips from close range.
Furlong was next to be thwarted as the Baggies looked to double their advantage.
Yet it was Charlton who levelled matters with 60 minutes on the clock, Bonne heading home from six yards after Bartley's block to deny Josh Cullen had inadvertently looped up into the air.
And matters went from bad to worse for the Baggies just seven minutes later as Ferguson was shown red for a challenge on Solly, despite referee Matthew Donohue initially dismissing Diangana.
Head Coach Bilić turned to Conor Townsend and Hal Robson-Kanu off the bench.
Cullen fired narrowly wide as the encounter entered the closing stages, before sub Robson-Kanu curled into the far corner with nine minutes remaining.
However, Cullen ensured it finished honours even when he slotted home an injury-time penalty, although Robson-Kanu fired over when sent through in the 95th minute.
Albion: Johnstone, Furlong, Ajayi, Bartley, Ferguson, Sawyers, Livermore, Phillips (Townsend 71), Pereira, Diangana (Brunt 88), Austin (Robson-Kanu 71).
Subs: Bond, Hegazi, Krovinović, Edwards.