How many times must I learn: check the errata for any published pattern?

This time, my lesson took about 2 1/2 hours of bewildered fussing.  It was my Lily of the Valley lace shawl — newly ressurrected and steaming along nicely.  Until the 2nd row I worked where I found myself one stitch short.  One missing stitch in a lace project could be a dropped stitch, a disruption of the yarn-over pattern, a total shift of the pattern one stitch to the left…So, I stopped and investigated.  I investigated and investigated.  I counted stitches, studied the knitted fabric stitch by stitch, texted Sarah, studied the pattern chart, tinked, studied, called Sarah, studied and counted again, 2nd guessed myself, hallucinated, sighed deeply, counted, studied….

And then realized that the chart was missing a yarn-over.  Four blank squares instead of 3 blank squares and a square with a little circle in it.  My knitting was right; the chart was wrong!  I dashed over to my computer and checked the publisher's errata page for that book and, lo and behold, there it was:  my missing little circle in bright yellow!  There was a missing yarn-over and a missing decrease 2 rows below too — which would not throw off the stitch count, of course.  But the combination of missing marks camoflaged the error — it just looked like the end of the lacey pattern at the edge of the triangular shawl (decreasing in width).

These things happen.  So, repeat after me:  I will always check the publisher's errata, I will always check the publisher's errata, I will always check the publisher's errata….

Note: for a book, check the publisher's website & there should be a "patterns corrections" page — for a magazine, check the magazine's website.  Sarah says: if you have set the project aside for a while, go back and check the errata even if you did so when you started out — someone may have found something in the intervening weeks, months.