Skipped meaning they are out of order from the others?
1
2
3
17
4
5
6
23
7
8
9
10 ?
Can you sort ascending or descending to find them? Look for duplicates?
You can get at this with Python:
>>> fc = 'points' # feature class/layer
... field = 'Id' # field to inspect
... start = 0 # first value
... stop = 25 # last value
... step = 1 # increment value
... present_values = [i[0] for i in arcpy.da.SearchCursor(fc,field)] # load present values to list
... missing_values = [i for i in range(start,stop,step) if i not in present_values] # compare present values to possible values
... print missing_values # print list, or do some thing with values
...
[0, 9, 15, 16, 21, 22, 23, 24]