Is haphazard the only word where ph is not pronounced like /f/?
No. Trying to find other examples is an uphill battle, though.
In greater detail: Words that came from Greek and have a 'ph' in a single morpheme tend to use the /f/ pronunciation (except some cases like "Stephen" where it's /v/ — voiced instead of unvoiced). However, words that were formed by combining separate morphemes (such as uphill, loophole, haphazard, etc) have a 'ph' that belongs to two morphemes and does not represent an /f/ sound.
Yes 'haphazard' is a unique word which has 'ph' and is not pronounced as 'f'(a few people may suggest 'amphitheater' as another word but I can't say for sure). However, there are several compound words where 'ph' doesn't sound like 'f' when pronounced. A few of such compound words are:
flophouse, loophole, peephole, uphill, uphold, upholster.