It's not plausible that such a large animal can have a self-sustaining population in the wild, and not be properly detected by the scientific community for 100 years.
Except that in general the "rediscovery" isn't something dramatic -- it's just a systematist in a lab looking at an animal known by many and realizing that it is the same species as fossilized/preserved specimens thought to be extinct rather than a common related species. That's quite different from finding a thylacine, an animal that couldn't be confused with anything else.
Bermuda Petrel -- there are many nearly identical petrels, exactly the same to non-experts.
Chacoan Peccary -- There are many wild pigs.
Coelacanth -- Maybe the only real example of a "rediscovered species". But that's only because we know the oceans far less than we know the land.
Lord Howe Island Stick Insect -- You've probably seen a stick insect like this yourself even if it is genetically different.
La Palma Giant Lizard -- Same genus as Gallotia, a very common lizard on the Canary islands.
Takahe -- It's the same genus as the swamp hen. To an non-expert, they are the same.
Cuban Solenodon -- it looks like a common shrew to non-experts.
New Caledonian Crested Gecko -- It's a geko.
New Holland Mouse -- it's a mouse (not a marsupial, despite being native to Australia).
Giant Palouse Earthworm -- It's an earthworm, although larger than normal.
Large-Billed Reed-Warbler -- same genus as many other warblers, exactly the same to non-experts who don't measure the bill.
Laotian Rock Rat -- It actually is of a unique genus, so more interesting than most of these examples, but still, it's a rodent not that different to the average person than other rodents.
In 1910 someone tried to introduce moose into a remote corner of New Zealand [1]. They haven't been seen since 1952, but seem to still be out there, as hair was found in 2002. If things as big as moose can hide a self-sustaining population in a small corner of New Zealand, thylacines could plausibly hide in Australia or Tasmania.
