And then there are those whose traditions teach that a person who has lost their salvation
CAN return to the faith, if certain conditions, set by the church, are met. This, in fact, is what most churches, who hold the position that salvation can be lost, actually teach
(which is why Hebrews 6:4-6 says way more than many churches, who believe/teach that salvation can be lost, wish it did )
The descriptive language used in Hebrews 6:4-5 is unusual, to say the very least. One thing is made perfectly clear however in Hebrews 6:6 (that you just pointed out above), if Hebrews 6:5-6 is actually talking about the loss of one's salvation, then v6 makes it abundantly clear that someone who loses it will never get it back.
--David