Should not be possible. You did use the timing tools (pin+plate), right? The focus is THE easiest car to time that I have ever worked on. For those that haven't had the pleasure:
1. Before installing cams, set the crankshaft to TDC using the pin (should have already set that during disassembly).
2. Install cams as close to TDC position as possible. Set to TDC using plate.
3. Set timing belt tensioner.
4. Torque cam gears without putting pressure on the timing tools (helps to have 2 people).
5. Remove TDC pin & plate.
6. Rotate engine via crankshaft through one or two revolutions.
7. Find TDC using pin again, check that plate still fits (shouldn't to wiggle cams much, if any).
8. Remove pin & plate, install TDC pin bolt, slap the valve cover & plugs back on, start-er-up.
You probably don't need this, but just remember: if you have air, fuel, and spark (at the right time), your car will start
Did you remove any fuses? Are they back in? Is every connector (cam position, coil, MAF, etc) connected?
SCT PRP FTMFW!