Think inputs and outputs
The key to this sort of puzzle is thinking about the inputs and the outputs. If you don't want the answer, look away now...
The simple answer is there is no missing $1.
The men paid $30 (the only cash input).
The hotel owner has $25, the men have $3 and the bellboy has $2 (the only cash outputs), totalling $30.
The question cleverly mixes up inputs with outputs - it's a beautiful example to use in training courses where you're trying to teach people about process thinking. In my limited experience, accountants get this problem straight away - almost everyone else struggles.