The hosts had to recover from the shock of going behind in just the fourth minute through a terrific strike by Anthony Grant but battled their way back into the match commendably.
Crewe got off to the best possible start as a corner was only cleared as far as Grant outside the box and he struck a brilliant first-time shot across Matt Ingram and into the top corner.
Against the run of play, Wycombe drew level as Cowan-Hall got in front of his marker to flick Dean Morgan's cross into the bottom corner.
The Chairboys almost went ahead just after the hour mark when Crewe goalkeeper Alan Martin had to push away Max Kretzschmar's powerful free kick.
Crewe then almost snatched it in the 90th minute as Brad Inman struck an effort over with Ingram beaten but these two will have to do it all again at Gresty Road in 10 days.