"Where is Iain? I do not know."
Translation:Càit a bheil Iain? Chan eil fios agam.
Not according to the latest research by Prof. Roibeard Ó Maolalaigh. He found statistically that the lenition was more common in the negative (with eil) than in the positive (with tha). eil is a very strange word and it is known from Old Irish that the apparent subject is actually in the accusative, and thus is the grammatical object. He knew from Old Irish, and you know from Welsh, that the object of a short-form verb (as they call it in Welsh grammar) is lenited. Weird, but each step in the argument is supported by evidence.
I had a look in DASG and Mark (2003).
fhios and agam are frequently run together to make fhiosam □ chan eil fhiosam fhathast dè bha fa-near dha I still don't know what he had in mind □ dh'fhosgail e dorsan dhomh nach robh fiù 's fhiosam gun robh iad ann he opened doors for me which I didn't even know existedand I found
and I found the following occurrences
(Note the DASG software cannot tell if there are spaces either side of the apostrophe.)
Of these, the last three are just different spelling conventions for one spoken phrase. The standard convention in modern Gaelic and Irish would be fhios 'am, although most other languages would leave the space out in something like this. The last one, that you suggest, is an irregular spelling, but actually more common than the other two contractions (which surprised me). Perhaps it is a hangover from earlier spelling conventions. DASG covers several centuries of data but Mark is a pretty good guide to late 20th century practice. So, with this evidence you or someone else can try 'my answer should be accepted' next time they get a chance. 29% in Mark, with a 'frequently' comment, cannot be counted as a rare variant.
Sadly I can't. Duolingo does not have the technology to slow down real speech such as is used in Gaelic. All the high-demand languages such as English, French, German Spanish etc. use commercially available speech software which is capable of slowing it down. This is not available in Gaelic so they use real people. This has both major pros and major cons. I'm sure they could find software to slow it down, but they appear to have neither found any nor hidden the slow-speech button.