The period (.key) for access on an object is sugar for normal table access using a string as a key (i.e., accessing using [key]).
a.b is considered by the interpreter to be doing a["b"].
So if an object has a space in its name, you can refer to it using that version, instead:
Object["Spaced Named"]
To underscore the concept, remember that you can use this always:
game["Workspace"]["Part"]["Transparency"] = 0.5
Alternative, you could use FindFirstChild since it always takes a string as a parameter to begin with (but is much more verbose).
Also, FindFirstChild does not return a boolean, it returns an object. All objects are truthy, though, which is why it is used in if statements.