In reply to minimike:
Don't panic - it may not be serious. Most cracks, particularly if small, are not.
In the first instance invite him back to comment. He may have seen it, and may not have been concerned. Ask to see his site notes which will show if he saw it and recorded it. Even if he didn't record it, it may still not be serious.
See what he has to say, and remember that you are still his client so he continues to owe you a duty of care in any further advice he gives you. Also if it's movement which has occurred since his survey, then in the (generally unlikely) event of your having to make any insurance claim his knowledge of it's condition previously may help your claim. Hopefully it won't come to that
If you feel unhappy with what he tells you, then is the time to get independent advice.
Trangia - Retired Surveyor
PS I would not expect a surveyor to charge for a re-visit in such circumstances.
Post edited at 10:50