Does retinal detachment happen more frequently at night? My understanding and experience is that during the night photoreceptors are less tightly coupled to the retinal pigment epithelium. Does this make it more likely for a retinal detachment to happen at night?

In case of normal, healthy person, no, I don't think so. In fact, retinal detachment could happen at anytime of the day. Main causes are diseases and illness, such as AIDS, diabetic retinopathy, cancer, or trauma such as post-cataract surgery and being hit/kicked hard on the eyes.