The question/query is this - is it likely that corrosion will have formed in the cylinders in this time
I'm not quite sure what the "time" is, other than 3 months? The possibility of corrosion is to a large degree dependent upon what type of cylinders the engine has. If steel, then yes, corrosion is possible. If chrome, you're probably okay. Ground running an engine is not universally thought of as a good practice for preventing corrosion. Flying the plane regularly is. If you know that flying will not be possible, inhibiting is the best thing to do.
If the engine has suffered corrosion, there's not much you can do about it now (and there will be no way to quantify, or assign responsibility for that, so it is what it is). Just fly the plane regularly. Cylinder corrosion is not good, but in Lycomings, it's camshaft corrosion which will cause the really serious and costly damage to the engine. However, you have zero way of knowing the condition of the camshaft, until you remove cylinders, so no point fretting about it unless the engine starts making metal. If the engine starts making metal, remove it from service right away (certainly don't fly it across parts of oceans!).
Engines are consumable - wear and corrosion, to whatever degree of each. They are consumed while being used (wear), and while being parked (corrosion). Ground running does little to prevent the consumption. Inhibiting does a better job.