Hold the throttle open just a TAD. Now try and start it. If it starts and you let the throttle go, does it immediately die? If so, your IAC valve is closed all the way. This was because the PCM noticed the idle was very high due to the disconnected vac line and it tried to compensate by closing the IAC(Idle Air Control) valve.
Usually the IAC valve can be reset by turning power on for about 20 seconds and turning back off without cranking. Then power back on and proceed to crank. If this doesn't work, you may have to force it to relearn while driving around 35 MPH. This can take some double footwork to operate the brake and the throttle at the same time.
1997 Pontiac Bonneville SEi-SCRAPYARD
2000 Chevrolet Blazer LT 4X4 4.3L
2002 Chevrolet *-10 LS Ext Cab 4X4 5.7 V8