Good try! But alas, no. :P
The PIV dictionary definition of pilko is:
Ĵetglobo, ordinare el pli-malpli elasta materialo, uzata en diversaj ludoj
(a throwing globe, usually made from more or less elastic material, used in various games.)
A meatball is "viandobulo", bulo being:
Peco de pli-malpli knedebla materio, kun proks. globa formo
(a piece of more or less kneadable material, with an approximately spherical shape)
"bulo" is also used for snowball (neĝbulo), a ball of thread (fadenbulo), a ball of dough (pastobulo), a lump of earth (terbulo), etc.
Don't feel bad. The correlatives are one of the least intuitive parts of the language, even though their structure at first glance seems admirably logical.
The -u correlatives (iu, kiu, tiu, cxiu, neniu) modify nouns to indicate things as selections from a group.
For example, "Kiu hundo?" - Which [of the] dog[s]? "Tiu hundo." That [one of the] dog[s]. But when these correlatives are left all alone without anything to modify, then the group we are selecting from is understood to be the group of people. So "Kiu?" is "Which [person]?" and "Tiu." is "That [person]." It is actually not very different from English. When I say "someone" the -one in question could theoretically be one of anything, but we all understand it to be one of us (people).