No fermentation, too warm?

I brewed a porter on Saturday morning, added the liquid yeast (no starter) from an inflated (somewhat) smack pack. The wort was at the correct temp when I pitched the yeast. The primary is in the basement, the air temp is around 75. There are no signs of fermentation (used Activator Scottish Ale) as of Tuesday afternoon, no bubbles in the air lock, and nothing on the top of the liquid. I placed the primary in an ice bath with a wet towel wrapped around it Tuesday afternoon. Is this going to be enough to get it down to acceptable temps? The instructions called for a fermenting temp between 70 and 55.

Is it ruined? How long do I let it sit like this? How do you get your beer to the right temps for brewing.

I have made about 8 batches and have not had this slow of fermentation yet. Thanks.

I've had one take four days to start and a friend told me he had one go 7. Stay patient.

No, your beer isn't ruined. It's very difficult to ruin a batch of beer.

Every batch you make will behave differently. 75F is more than likely fine for the yeast you're using, regardless of what the pack said. The reason it said not to ferment that high is that you'll have fruity off flavors because of the high temps. It won't likely be enough to ruin your beer, but it's something to watch in the future.

Have you taken a hydrometer reading of your beer? It's possible that it's working away, just not showing any visible signs yet. The airlock is not an accurate way to read your beer. Sometimes they won't even bubble. If your gravity hasn't gone down at all, then you'll need to repitch another pack of yeast or try to get the current yeast back into suspension. You can do this by rocking the fermentor a little bit.

As for controlling temps, there are numerous ways to do it.
A. Put a wet t-shirt over the carboy (assuming you're using a carboy and not a bucket) and leave it in a tub of water. Have a fan blowing on it. As long as the t-shirt stays wet, it'll keep your beer about 5 degrees colder.
B. Put the fermentor in a tub of water and add a few frozen 20oz bottles to it. Keep an eye on the temp. It should drop the temp 10 degrees or so.
C. Invest in a cheap fridge or freezer on craigslist or new (whichever you can afford) and add a temperature control unit to it. This is what I do, and it's by far the most accurate way. You'll also be able to do lagers with this method.

You should be fine. That temp isn't high enough to kill the yeast. Keep temps stable and you should see some action.

Most importantly... https://www.homebrewtalk.com/f39/fermentation-can-take-24-72-hrs-show-visible-signs-43635/, and by visible signs we don't necessarily mean a bubbling airlock.
It IS a sticky at the top of the beginners forum for a reason, afterall.

Especially since you didn't make a starter, which would have got the yeast up and running...

Wait 72 hours and take a hydro reading.. And you'll find that you worried and for nothing.