For some reason I can't get \textpos to place anything snugly against the upper left corner of the page -- if set the position to (0,0), it still seems to leave a small amount of space above and to the left. However, with a bit of tweaking I was able to get a horizontal rule the size of your image to center pretty well (perhaps not quite perfectly). The hacked LyX file is below.
Paul #LyX 2.0 created this file. For more info see http://www.lyx.org/ \lyxformat 413 \begin_document \begin_header \textclass article \begin_preamble \usepackage[absolute]{textpos} \end_preamble \use_default_options true \maintain_unincluded_children false \language english \language_package default \inputencoding auto \fontencoding global \font_roman default \font_sans default \font_typewriter default \font_default_family default \use_non_tex_fonts false \font_sc false \font_osf false \font_sf_scale 100 \font_tt_scale 100 \graphics default \default_output_format default \output_sync 0 \bibtex_command default \index_command default \paperfontsize default \spacing single \use_hyperref false \papersize default \use_geometry true \use_amsmath 1 \use_esint 1 \use_mhchem 1 \use_mathdots 1 \cite_engine basic \use_bibtopic false \use_indices false \paperorientation portrait \suppress_date false \use_refstyle 1 \index Index \shortcut idx \color #008000 \end_index \leftmargin 3cm \topmargin 2cm \rightmargin 3cm \bottommargin 2cm \secnumdepth 3 \tocdepth 3 \paragraph_separation indent \paragraph_indentation default \quotes_language english \papercolumns 1 \papersides 1 \paperpagestyle default \tracking_changes false \output_changes false \html_math_output 0 \html_css_as_file 0 \html_be_strict false \end_header \begin_body \begin_layout Standard \begin_inset ERT status open \begin_layout Plain Layout \backslash newlength{ \backslash temp} \backslash setlength{ \backslash temp}{ \backslash parindent} \backslash setlength{ \backslash parindent}{0pt} \backslash begin{textblock*}{11cm}[0,0](5cm,0cm) \end_layout \end_inset \begin_inset CommandInset line LatexCommand rule offset "0ex" width "11cm" height "4cm" \end_inset \begin_inset ERT status open \begin_layout Plain Layout \backslash end{textblock*} \backslash setlength{ \backslash parindent}{ \backslash temp} \end_layout \end_inset \end_layout \begin_layout Standard Here is some text, hopefully indented. Blah blah blah blah blah blah blah blah blah blah blah blah blah blah blah blah blah blah blah blah blah blah blah blah blah blah blah blah blah blah blah blah blah blah blah blah blah blah blah blah blah blah blah blah blah blah blah blah blah blah blah blah blah blah blah blah blah blah blah blah blah blah blah blah blah blah blah blah blah blah blah blah blah blah blah \end_layout \begin_layout Standard This starts another paragraph. \end_layout \end_body \end_document
