Actually, it seems it was me and CantoDict that was doing the mixing-up. I was reading the expression 騫翁失馬 as "hin1 jung1 sat1 maa5", as it's entered in CantoDict, and she was adamant it was wrong. It should be read as "coi3 jun1 sat1 maa5". Seems that's indeed 塞翁失馬, which is the expression that's listed in Pleco. For some reason, CantoDict has these four:
塞翁失馬
塞翁失馬,焉知非福
騫翁失馬
騫翁失馬,焉知非福
The latter two are not in Pleco. Are we sure they are correct?
塞翁失馬
塞翁失馬,焉知非福
騫翁失馬
騫翁失馬,焉知非福
The latter two are not in Pleco. Are we sure they are correct?