It seems to be now fashionable to use the word plausible to hint at two words:
Possible, meaning a thing can exist but it in fact does not exist -- like for example because no one has yet invented it.
Probable, meaning that it can be proven to in fact exist or to have existed, but there has not been found evidence of its existence -- yet, or evidence will never be found.
Read these entries from the Online Etymology Dictionary, http://www.etymonline.com:
mid-14c., from Old French possible and directly from Latin possibilis "that can be done," from posse "be able" (see potent). possible (n.) 1640s, from possible (adj.).
late 14c., from Old French probable "provable, demonstrable" (14c.), from Latin probabilis "worthy of approval, pleasing, agreeable, acceptable; provable, that may be assumed to be believed, credible," from probare "to try, to test" (see prove). Probable cause as a legal term is attested from 1670s.
1540s, "acceptable, agreeable," from Latin plausibilis "deserving applause, acceptable," from plaus-, past participle stem of plaudere "to applaud" (see plaudit). Meaning "having the appearance of truth" is recorded from 1560s. Related: Plausibly.
Do you notice that plausible originally had nothing nothing to do with the existence of a thing in regard to whether it can exist or not (possible existence), or whether it really in fact exists or had existed, but there has not been found evidence (probable existence).