The boiler may have an automatic ignition - there must be a button to press to light it. If it doesnt have on it may also have an auto pilot igniton.
However if the pressure in the system has dropped for any reason, the pilot will not light automatically or by pressing a button. Check your pressure reading on the dial and see what it says. Get the handbook and see what your boilers operating pressure is. You may need to fill the system from the cold water loop if the pressure is too low, this will increase the pressure in the system and your pilot light will light. If you are not sure - decent plumbers would only charge you a call out to get it going again if all it needed was refilling - it's a ten minute job.