I have an Echinocereus salm-dyckianus, and my neighbors son just pulled all four flowers off of it. How can I get it to flower again?
Did you notice any little buds coming? If these four were all it was going to put out at this time, some cacti will flower again, usually soon after the first ones, or they will want to rest, after spending the energy to flower. If time goes by, and no more flowers, I'd safely say it is indeed resting. Unfortuntely, there's no real way to tell if this particular one flowers only annually, or quarterly, etc. Remember to keep it root-bound - this forces flowers in lots of plants, beside cacti. If you determine it is indeed resting, withhold watering even more than normal.
I'd give it a 2-3 months to kick back, then you can try and increase watering, just by a hair! and see if that kicks it back into flowering mode. Hope this helps!