G. W. Fuchs, U. Fuchs, T. F. Giesen, and F. Wyrowski,
Trans-Ethyl Methyl Ether in Space
A new Look at a Complex Molecule in Selected Hot Core Regions
Astron. Astrophys. 444, 521530 (2005)
have searched for quite an extensive number of EME transitions employing the IRAM 30m and SEST 15m telescopes. A small number of 3σ transitions plus some less significant transitions were observed toward W51e2. The most probable column density and rotational temperature are compatible with values for related molecules. Moreover, the spectrum synthesized from these values is compatible with all observed lines. However, since the number of significant lines is still small the detection should be viewed with some caution.
Upper limits only were found toward G34.26, NGC 6334 I, Orion KL and Sgr B2(N).
P. B. Carroll, B. A. McGuire, G. A. Blake, A. J. Apponi, L. M. Ziurys,
and A. Remijan,
The Search for a Complex Molecule in a Selected Hot Core Region:
A Rigorous Attempt to Confirm trans-Ethyl Methyl Ether toward W51 e1/e2
Astrophys. J. 799, Art. No. 15 (2015).
The authors point out "missing lines", thus disputing the claim of a tentative detection by Fuchs et al. Moreover, they mentioned errors in the derivation of column densities in the above work.
Overall, ethyl methyl ether should be viewed as an undetected molecule even though prospects of detecting it eventually may be fairly high.