Now, it's all starting to make sense. I find the Hi-Vis Gold line I've recently used is one of the exporting products from the US! I was thinking it was strong enough, but it is only 10lb-tested as a US norm. I should have paid much more attention to that; as sizes differ between countries, strengths of lines are also differently rated.
In the US, a line comes in the strength (lb test) by which the line is never broken when it is pulled in both directions. In other words, it is shown not by the strength of line itself, but by the strength of the weakest 'tied part (knot)'.
In Japan and the IGFA standard, a line is shown by the strength by which the line is surely broken when it is pulled. When you tie it, the connecting part becomes weaker, even if you use a strong knotting method. I've once read that a Palomar knot (one of the most popular knotting method in the US) shows up to about 90% strength of the original line, and others show worse results, suggesting that exporting products are one or two-class thinner than domestic ones.
For my future reference, in Stren lines:
14lb (US rated) = 20lb (outside US), 0.014" dia (=0.36mm, #4.5 or 5)
12lb (US rated) = 17lb (outside US), 0.013" dia (=0.33mm, #4)
10lb (US rated) = 14lb (outside US), 0.012" dia (=0.29 or 0.30 mm, #3 or #3.5)
I mostly use 12lb or 14lb lines (US rated) when I bass fish with my topwater lures, but the line I was using when I lost my lure last time is now found 10lb. Of course, a 10lb line is strong enough to fish with and for fishers who recognize it as 10lb, but I had used it as a 14lb tested line in weedy areas. A complete failure of mine.
I must therefore resume my fishing style, and went fishing early this morning. All in all, thicker lines are stronger and more dependable, though I could not catch a big fish.
Today's tackle: ABU Ambassdeur Royal Gold LE, Mr Don MW59N (Dog Fighter) w/ Fuji wood grip, Stren Low-Vis Green 12lb, Heddon Zara Spook, Chugger Spook, Hedd Hunter Minnow (w/ prop), Southbend Nip-I-Diddee, Smithwick King Snipe, etc.