I don't have a Tiscali account so can't help much further but have you looked at this guide from Tiscai which says that it will show you how to personalise your settings. It may show you how to restore a missing Spam folder.
I, too, am with tiscali, and have been for more than 10 years; although I am glad to say not for much longer. You are very lucky getting so little spam, as I can get up to 38 emails per day and about 32/33 of them are spam. I mark them as spam, and tiscali are supposed to block them but all it seems to do is to encourage the spammers to send more.
What I have found much more worrying is that some emails are directed straight into not the spam box, but the delete box. What is even more worrying is that having looked at my emails, deleted some of them, some of the ones I wish to keep have gone the next time I log in. I usually find these in the delete box, but others have just disappeared. How and why this happens I have not got a clue.