Using as instead of the standard relativizer that is a relatively common "dialectal" feature - particularly with negated stative verbs such as know, see, feel...
1: We don't know as we believe him.
2: He can't see as it matters whether we believe him or not.
3: I don't feel as I trust him.
Although competent native speakers know perfectly well this usage is "ungrammatical", some of us use it occasionally to add "folksy" authenticity to a negating / demurring utterance. But others just do it because they're ill-educated, so I wouldn't advise non-native speakers to copy the usage lest they be mistaken for that latter category.
The other "marked" aspect of OP's cited text is the stylistic "inversion" ever I was lost, which would normally be expressed as [I can't say that] I was ever lost. This is more of a "poetic" usage than a "dialectal" one - but since the context here is folk hero Daniel Boone, it's not inappropriate.
The construction I can't say that [statement X] is an idiomatic usage normally implying a degree of hesitancy about baldly asserting that X is not true (as in the cited example). Sometimes the speaker really does want to "weaken" his assertion in this way, but sometimes it's a "sarcastic" usage that actually emphasises the degree to which the speaker rejects proposition / statement X.
To paraphrase the cited text...
I was never actually lost, but once it took me a few days to figure out where I was.
(Most people would say that if it took you days to find your way out of the wilderness, you were in fact "lost", but Boone humorously avoids having to explicitly admit that.)