Hi,
555 can be used as a missing pulse detector, only need to add a BJT, page 13, 9.2.1 of the attached pdf, the description reads:
"The circuit shown in Figure 16 can be used to detect a missing pulse or abnormally long spacing between consecutive pulses in a train of pulses. The timing interval of the monostable circuit is re-triggered continuously by the input pulse train as long as the pulse spacing is less than the timing interval. A longer pulse spacing, missing pulse, or terminated pulse train permits the timing interval to be completed, thereby generating an output pulse as shown in Figure 17."
Frequency is usually not too high with a 555, 100kHz for the SE and SA and NA types, etc., but it doesn't cope so well at so high a frequency, and the LMC555 says 3MHz, I hate to say anything negative about the 555 but without having tested an LMC at that frequency I would take that with a pinch of salt or assume "datasheet optimism."